I worried about this, too. Does having a little extra magicka or stamina counter-balance the lower armor ratings? I had a templar with nearly-full heavy armor and I was perpetually out of magicka (and often stamina, since it's used for blocking/interrupt, running, sneaking, etc)... so the extra armor was nice, but since I had no resources to DO anything, I had a tough time. Granted, this was at lower levels and at higher levels I could have gotten passives and such to help resource management...
I don't generally care for the look of heavy armors, but it's hard to argue with that big high-armor value when comparing two pieces. In the last beta, I was surprised to see I was "overcharged" (or whatever it said) for magicka regeneration. Not sure HOW that's possible, but it was in orange text, warning me I might want to re-allocate stuff... nice feature, that.
At least Heavy armor belts and helms (which can be hidden) aren't too obvious, and that leaves five armor slots for light or medium that, cosmetically, I prefer.