Here's my $0.02 - I think you can get a pretty good idea of what a hops will taste like by its dry aroma. Of course the flavoring of a bittering hops is best learned by taste. My personal opnion is that the best way to experience them is in combinations from IPA clone recipes. While its not a pure comparison, you still get a pretty good feel for the individual hops flavors and also which ones complement each other well and in what proportions they're best used.