Based on my recent research there are broadly 4 classes:
- Competition gloves
- Sparring gloves
- Bag gloves
- Specialty gloves
Competition gloves tend to be about 10 oz, although it depends on the competition. The important thing is that you don't wear your own gloves at fights, they provide their own. You might think about buying similar ones anyway, to train in a "realistic" way, but the issue is that usually they will be laced gloves which you need help to tie. So not good for training.
Sparring gloves are 16 oz or more. This is not so much to do with the effectiveness of your training, but more about protecting your partner from injury. People spar with very padded gloves, but it's because they're hitting another person not a bad, not because the heavy padding is necessarily better for their own gains.
Specialty gloves usually look very obviously unusual, they will be for some narrow purpose. If you're not looking for them specifically you probably want to avoid these.
With bag gloves, the main concern is the effectiveness of your training. I consider health and safety part of this, because if you break your wrist you will not be training effectively. In this case you have two options:
- You can get heavier gloves, like 16 oz, to have more padding. I'm biased towards less padding because I'm lucky with hand pain. So I would say this is a good choice if you've had a tendency to have pain with other gloves.
- My own decision was to go for "medium" padding at 12 oz. The advantage of this is that the gloves are lighter, and go faster, so you can train with more realistic speed and pace compared to what you would have in a fight. Of course, if you don't care about realism but are doing a specific drill, this doesn't apply.
In this post I use numbers like 10, 12, 16 oz but actually these vary with your size. Heavier gloves are usually also bigger and roomier. The fancier boxing glove makers will have detailed sizing guides on their side explaining how to measure your hand and so on. Also, I've heard of people getting one size higher or lower depending on the additional bulk of their wrist wraps. So in reality these numbers would depend. The 10-12-16 is usually for "average/medium" people.
Also, a lot of generic sports good stores have bad or incorrect categorization of boxing gloves. Whereas the ones that sell only boxing gloves, and are well regarded brands ($$$ too of course) have very sensible categories like "bag gloves", "sparring gloves" etc. So I think it's helpful to look at those even if you're not planning to buy from them, just to understand the product you are shopping for. With cheaper stores it's very confusing.