I have a 90 auto ex sedan, and it serves me well...
If you're going for a buncha mods, go with the hatchback. Most of the aftermarket parts made for 4th gens are for the HB. Taillights, bodykits, etc.
I had the option of buying either a sedan or hatchback, both for the same price. I went with the sedan because it just looks nicer to me, and i could get more use out of it cuz i carry people around a lot, and it would suck for me to hafta get out and fold down the seat everytime we park somewhere. The sedan doesn't have a whole ton of aftermarket, but it's enough to keep me busy. Besides, if you don't like the Xtreme bodykit, just go with cardboard.
One question you hafta ask yourself is, auto or stick? If you can drive a stick and you plan to do performance mods (which sounds like what you're eventually going to do), go with the HB. I go with the auto cuz i'm a lazy bum (and the civics don't come with dang cup holderz!)
But really, it depends on what you want out of your car. If you carry people around a lot, go with the sedan. If you don't, get the HB. Or if you don't like either one, go buy a dodge stratus with the transmission that fails 2 months after you buy it, lol.