I was surprised with one of these L4S models under the tree yesterday (yayyyy!) and just wanted to let everyone know that it came with a little pamphlet describing all of the Huion models. While the Amazon pages can be confusing, it turns out the differences in size/accessories are easily understandable when you have pictures of all of them with the specifications of each!
They should really publish thumbnails of this pamphlet on their product listing pages. Anyhow, if anyone has a particular Huion model in mind and want to know exactly what size it is and what it comes with, let me know!
For now, I think the most important distinctions are that the L4S and LB4 include a USB cord that must be plugged into a computer or a wall adapter for use, but the A4, A3, and A2 all come with a regular power adapter that plugs into the wall. I think most people have either a computer or a USB adapter, but if you don't you should know the LS4 and LB4 do not come with one. (Huion does sell a USB adapter on Amazon for around $12.) The LB4 also has a battery pack, which is why the outer dimensions of the pad are different than the L4S's but the active area is the same-- (see my question and links two posts up). They are all made by Huion, which is apparently a Chinese company per the info on the box and pamphlet, so that's probably why there are various grammatical/spelling errors in the listings.
All in all, seems like a great product and a good investment for anyone looking for a light pad!