[Kromm]

I'll say only that "I have to punch 30 holes in this one piece of plate armor, which might be enchanted to be harder to punch holes in, to make just that one bit less magical" seems like a more daunting challenge than "I have to steal this guy's ring to completely negate the magical protection it provides to his whole body." In the case where you're a crap thief, there's always simply chopping off the ring-finger . . . that's one penetration.

Yes, there's a downside to having to wear a suit of plate armor rather than a ring: It's much, much heavier. But the extra weight is also doing something, which is providing you with DR 6 regardless of enchantments, so I'm not sure that's a real drawback.