From: Lucian04 | #003 You can only wear one or the other. I did the game with neither armor, there honestly isn't any need for either of them.
my first play thru i didnt even know armor existed. this playthru i got the stealth suit. and wow. stealth suit isn't useless. you can do all the stealth without it sure, but the suit makes it much easier.
cant say much about the damage armor, i havent really tried it.
I used the heavy on my first run and the stealth now. The heavy is nice when you are being swarmed, or you tend to run and gun areas. The stealth suit simply makes sneaking that much easier, though you are still screwed once the enemy notices you.
After trying both, I'd say what I'd tend to do is take the stealth suit when its available and the trade it out for the heavy armor at Polis station, since sneaking is much less useful when dealing with mutants.