If you played FF1 - 6 and liked it you should get 7 as well. If you didn't like them (why the hell did you play 6 parts then?!), then don't get 7.
Now the main question was if you should get the steam release anyways.
If you want to pay for it and want to "own" it, do it.
Otherwise the steam version won't be anything special, I heard you can buy level up packs or something (for real life currency) in that version, but yeah that's nothing I would call a deal breaker or anything, it's just an option for people who don't want to level, I guess.
