It's personal preference really. I won't go back to plastic if I can help it. Least not with Apple, they seem to have a problem with their plastic stuff cracking (everyone with my macbook that I knew of had cracks on their handrests and even elsewhere and even the iphone 3G I had apparently there was issues with cracks forming. So I don't trust Apple to either use decent plastic or a form that doesn't stress the plastic too much).
At least with the metal stuff I can be careful and prevent damage. With the plastic, it just seemed to happen (stress cracks basically). And poster above me reminded me. Almost a year with the MBP, it still looks clean. You should have seen how nasty the plastic on my MB looked (after a year it was starting to form stains where the hands were, by three years it was gross).
And I hate white on electronics. It looks really stupid imho (makes it look like a cheap appliance).
