They're softer, have far less backbone than boar and create lather a bit faster. Aside from pure badger which is basically black and pretty prickly to start with there isn't that much of a difference from one grade to the next if you ask me. It's only looks really. Yes, silver tip/two band does look good. Unless of course you've paid $400 for a three band Manchurian High White badger knot, then there simply has to be a huge difference (about $200 worth because that's how much you get ripped off by). There is no difference to how they work from the humble black or pure to what ever grade you choose.
I've got six brushes and only one of those is a boar and one is a boar/badger mix. So I guess I prefer badgers, but that might be because, unlike boar, you can get badger knots in a variety of sizes which I plonked in a variety of obscure handles.
If you're thinking of getting one, on the whole do not go too big or too dense and it'll be dandy. The Berkley that Drubs had/has for sale would be an excellent choice. Basically a middle of the road Simmo in best. There are other makers out there but I only really know the Simmo range myself.
Oh, and if you document your shaves in an Excel spreadsheet, this conversation ends right now.