20.5 is going to be a bit small for you. You should look at something like a 21 up to a 21.25. As far as things to avoid, Eastern was always bunk in my experience. Although I haven't seen/handled any of their stuff in a few years.

As for maintenance and all that, its basically all the same. Bikes is bikes. The only thing that you might find different is the BB cluster/assembly, because the bearings are larger, and the cranks are a bit different than something for road or MTB use.