I agree with everyone above and second the statement that newspeedmaster.com is a good site - they've treated me well.
The colors, engine color, seat and handlebars are the main differences between the two bikes you need to consider.
If you're dead set on one engine color or the other that will dictate the bike you get as everything else can be changed (at a cost).
Some dealers will swap gas tanks between bikes if you want an America's shiny engine with one of the speedmaster color schemes or vice versa.
The seats are interchangeable so if you were to buy a speedmaster you could change to the America setup for some extra bucks. I also highly recommend the sissy bar for pillion riding. Well, my wife does.
Handlebars can also be changed to match your style and there are a million handlebar designs out there.
I guess in summary you're going to get roughly the same performance out of the two bikes so if neither one is quite perfect as is I would use the list above to narrow down.
Have you seen the colors available for the 2009s or just the current 2008s? I know the '09s will have new colors including a matte finish but don't know what the colors are. I've also heard rumor that there will be some new quick-release windshields and possibly a quick-release sissy bar in the 2009 range (which will hopefully fit older models as well).
If you are thinking to buy new you might wait until nearer the first of January when the new bikes begin shipping and see what the other updates are and whether the 09 or 08 strikes your fancy more. If you choose the 08 you'll probably get the better price but might as well have the wider selection to choose from, as well as the possibility of new accessories!
Best of luck! Oh, and where are you from?!
