The original GBA (I have the black TRU one) is more comfortable to me, but that's probably one of the few good things I can say about it. Battery life, screen brightness, screen crispness, and pocket-friendliness of the Micro made me put my original GBA back in its box. The Micro also doesn't feel cheap and plastic-y to me like the original.
I think that changing Micro faceplates is more the novelty, but I only have the Famicon plate.