So, having a 16 as opposed to an 18 in an ability causes you to suck? If that's the case, then the system is busted. And if you suggest that every character has to start with a 20 in their key stat in order to compete then that's even worse. Because that means you MUST play a class that your race has bonuses in, humans aside. Not only that, but with the current point buy system, giving yourself an 18 is a big sacrifice, if you do that, even your secondary attribute is going to suffer. Plus, the default array that they suggest gives you a 16 as the top. If that cause you to suck, then that sucks.
So, basically, you're trading a 5% to hit chance for the ability to wear armor. Yeah, I know it effects damage and other things as well, so will the increase in Str and Con. But, really, if playing a character with a 16(at 1st level) in his key ability causes you to suck, then I don't expect to be playing 4e long.