Its important to know that no matter what bin you use you can have success.
Its going to come down to what will be best for you. To help you make an informed decision, lets review the different kinds of worm bins available, why you might pick one over the other, and my recommendation for a specific bin for each type - each of which I have used personally.
Types of Worm Bins
For home worm composting, there are 4 types of Worm Bins
Continuous Flow Through
Batch Systems - usually DIY
Continuous Flow Through Bins - The Urban Worm Bag v2
Contiunous Flow Through Bins, or CFT bins for short, are generally accepted as the most efficient type of worm composting systems and the most similar to the natural feeding habits of epigeic earthworms. Professional worm casting operations almost always use CFT systems.
A CFT bin is designed so that food and organic matter can be added at the top of the bin, while worm castings can be harvested from the bottom of the bin.
Using a CFT you can continuously add food to the top, without the bin ever filling up because you are simultaneously taking material from the bottom.
The Urban Worm Bag v2
My top recommendation for a CFT bin is the Urban Worm Bag 2.
CFTs are generally the best worm bins, and I really don’t think you could design a better CFT for home worm composters than the Urban Worm Bag.
I like it, besides the ease of a CFT system, because its built out of a breathable fabric material and it will help beginners to make sure the worms and the bin gets proper aeration, which is huge. The source of almost all problems in a worm bin is lack of airflow, so this will help tremendously.
I also really like that it seals itself completely - whatever is in the bin will stay in the bin, and whatever is out of it will stay out. Other bins that are not built like the UWB have holes in them that can allow fruit flies or other pests to travel in/out of them.
And of couse since it is a CFT it is very easy to harvest worm castings when that time comes.
Its about 27” by 27” length and width, which means it can house at 4-8 pounds of worms, and process plenty of material - about 2-4 pounds a day, and of course, make more worm castings which are really easy to harvest from the base of the bag.
It can hold about 5 cubic feet of material, which is much more than other similarly priced options.
To top things off, it comes with a 100% lifetime warranty on material defects and guaranteed workmanship.
Things to Consider with the Urban Worm Bag:
Its not very mobile. Once you place it somewhere, you will need a second person to help move it.
The zipper at the base used to be difficult to use, but that has been updated since version 2.
Stacking Tray systems are just modified CFT systems.
They are composed of a number of plastic trays. Each tray has a bottom that allows worms to travel through the bottom of the tray.
Once the worms have eaten all of the material in their current tray, another tray is added on top with more food, and the worms will migrate vertically into the new tray in pursuit of new food. Eventually, you will be able to take out the bottom tray - which should be all finished vermicompost, empty it out, and continue to add trays on top, and take trays from the bottom.
The Worm Factory 360
My recommendation for a stacking tray worm bin is the Worm Factory Basic or Worm Factory 360.
The Worm Factory is the original stacking tray worm composter, a lot of other tray systems copied their design.
Although it is built out of plastic and doesn't have the same breathable material as the UWB, the base has an area where excess water can be released, making sure the bin doesnt get waterlogged.
Its also really fun to lift up the top couple trays and look at how the worms are doing deeper in the bin without having to dig up the bin.
When its time to harvest, its easy to take out the bottom tray, harvest it, replace it on top and repeat the process.
The Worm Factory also comes with bedding included as well as other resources to help you get started worm composting.
The Worm Factory is somewhat smaller - about 18 inches by 18 inches. This will make it easier to designate room for it, or move if you need to. It can hold 2-4 pounds of worms, and process 1-2 pounds per day. If you want something smaller, or don’t need to compost as much, the Worm Factory is a great pick.
Things to Consider With the Worm Factory:
The Worm Factory 360 is the same as the Worm Factory Basic, but it includes an extra tray and some other extra tools.
A batch system is one that has no continuous flow aspect to the worm bin - something like a plastic tote where worms and organic matter are added until its full, at which point, the entire bin is taken out, and harvested all at once - in one whole batch.
Batch Systems are generally accepted as the least efficient worm bin set up.
Batch Systems are usually very basic DIY bins. Now just to be clear, I am not talking about DIY Bins as a whole here, because theres an infinity of DIY bins you can make in all different styles, so I will strictly be talking about the concept of a batch system, which are usually a very basic DIY bin like this plastic tote, so I will use the term synonymously in this context.
There are no advantages to a batch system, other than the fact that they are usually DIY bins which are cheap or free.
They can also be any size or shape.
You can totally get creative with it, people use old freezers, old bathtubs - remember, the only thing a worm bin needs to do is
keep them in a confined location, and not inhibit worm’s other needs, temperature, food, water, and air.
The main downsides to a Batch system is that they are a bigger ordeal to harvest worm castings. When you harvest you have to do the whole bin at once, which means it all has to be ready, its more disturbing to the worms, and you have to restart the bin when you're done.
The downsides to basic DIY systems (which are what most batch systems usually are) is that they have less room for error. Specifically water and air are harder to keep in balance throughout your bin when your are using something like this plastic tote.
Especially as a beginner it is likely that you will overfeed or overwater your bin, and you will see the effects of those mistakes somewhat amplified in simple diy bin, and it will be a bigger ordeal to harvest worm castings when that time comes because you have to harvest the entire bin at once, and restart the bin when you’re done.
Theyre just not optimized for worm farming like other bins, but they can still work as long as it keeps the worms in a confined area, you’re okay to do more work harvesting worm castings, and as long as you make sure between the design of the bin, and your personal efforts, that you keep moisture and oxygen at the appropriate balance.
Be sure to have a source of ventilation for your worm friends - do not use anything thats airtight or has a lid without ventilation holes.
Again with DIY bins there is an infinitude of options, so I won’t talk about them all here, but I'll have a DIY worm bin guide in the guides at some point.
In Ground Compost Systems - The Subpod
In Ground Composters are systems that are partially submerged into soil.
These stand out from the others because they are exclusively outdoors.
The idea is that worms can eat food in the composter, but then leave it and travel into your garden soil, where they can aerate it, leave worm castings, and improve soil health. Additionally these will attract native earthworms who will do the same.
The Subpod is the top in ground composter available.
The Subpod allows your composting worms and native earthworms to travel directly into your garden soil and deposit worm castings there and aerate the soil.
Because it is outdoors you won't see the consequences of neglecting it effect you as much. If you neglect an worm bin and mismanage it, you may have worms try to escape the bin or may experience odors/pests inside. This does not happen if you manage your bin well, but if you're worried about not having enough time to take care of your bin, the subpod could be a good choice since it is outdoors.
**And to be clear - indoor bins can also be neglected for extended periods of time if they were not mis-managed prior to the period of neglect.
Because it is somewhat buried, it will survive the winter easier than other bins if they were left outdoors.
It has a horizontal migration system (like the vertical migration system of the worm factory, but horizontal instead).
The Subpod comes in two sizes - regular and mini.
Things to consider:
The conditions in your worm bin will be mixed with the conditions outdoors. Your worm bin wont be purely worms and waste and worm castings, but may become a mix of compost worms, native worms, other decomposer critters, and any other conditions that may be particular to your garden.
Though it is low maintenance, it is not immune to the potential cost of lower productivity that comes with lower maintenance.
Even though it is somewhat buried, it is still subject to temperature extremes. Worms will slow down productivity as they are colder, and may die in the winter.
Since the worms can leave freely, you wont have as dense of a worm population in the subpod (unless you maintain it well), and you won't be able to easily harvest as many worm castings because the worms aren't depositing all of their casts in that location (which can be a good thing because they're doing it in your soil.)
If you have the space for it, I'd look at the Urban Worm Bag 2.
If you don't have as much space, or don't need to compost as much, I'd look at the Worm Factory.
If you need to save money and recognize that you will need to take extra caution in taking care of your bin, I'd look at using a DIY bin.
If you 1.) need to do it outdoors 2.) don't want/need to worm compost all year as worms will survive, but are going to slow way down in winter 3.) don't mind worms being able to leave their bin, and other critters from your garden being able to enter the bin 4.) think that you'll have to neglect your worm bin for extended periods of times (weeks or months at a time) or 5.) only want to use the worm castings for the garden/soil area you are putting it in, I'd look at the Subpod.