Chrome all the way. Chrome-chrome-chrome-chrome-CHROME. You will be SET with some 20" chromes. I have an uncle who put polished aluminum billets on his mustang, and they looked really good. For a few months. After a few rainy days, they looked like a set of old, cheap, ugly junkyard saucers.

 

Both rims have their own good and bad qualities. Chrome is easy to clean and keep looking new. Many chrome wheels are subject to the chrome chipping off and that is not an easy fix. Polished wheels require a bit of work of polishing to keep them looking good. Scratches on polished wheels can be repaired much easier than chrome. IMHO, both look good.