Gort
Explorer
Plate profiency was the first feat I got for my Human Fighter. Why would I not want the best AC possible for my Defender?
Personally, I never go for plate on a fighter. I find the -2 armour check penalty too debilitating for the benefit of a single point of AC.
I suppose it all comes down to how much you value your physical skills, how many times you're going to get attacked on your AC, and what else you could have spent that feat on.