when looking at the metro DC area, you really want to live as close as possible to where you work. MD is ok, not like VA but unless you have a serious need for CCW or order ammo online, I think you will find MD to be fine. As one other poster said, if you need hi-cap mags, just drive to PA (or even VA) and buy as much as you want. You are allowed to own evil black rifles, you just have to wait the required waiting period.
The thing that prevented me from movig to MD from VA for a new job was that I buy a lot of ammo online and most places won't ship ammo to MD for some reason. I don't want to be tied to buying ammo locally from Dicks/Walmart or some gunshop where usually the prices are way high.