"Polished" gets its shine by polishing the alloy rim, while chrome has a layer of shiny metal electroplated on top of the rim. The chrome is definitely brighter and flashier. If the rim gets scratched, as mentioned above, it can easily rip right thru the chrome plating down to the base rim. So, from purely a "driver friendly" point of view, the polished rims are the better bet. From a pure aesthetics view, opinions are mixed ... some peole love chrome wheels, and some think they can be "a little much". Personally, I prefer the slightly more subdued look of polished over chrome but that is only a slight opinion -- there are lots of guys here who have chrome rims with very hot looking cars.
Just my $0.02...