I can offer my opinion on the R3 vs the Bird, tho i rode the regular R3. From what i have read at the R3 forums tho, the roadster dispute the bigger numbers doesn't perform as well as the discontinued regular R3. But in any case, If i had to recommend one or the other to you my answer would be is huge power and speed are of utmost importance to you, get the roadster. If not i'd strongly suggest the bird. Some reasons are subjective, some are not. The Tbird is almost w/o a doubt the best handling cruiser on the planet. There are sportbikes guys who have ridden or bought one and said it's in the same league aside from peg clearance, which isn't a big deal except in very slow speed corners. I've heard bonnie and even thruxton owners say thier new Tbird handles better. I'm here to telly you after 15000 miles, they aren't exaggerating. So handling is a huge plus IMO. There are a lot more reasons, but i'll leave it at that because a lot of it is subjective. Handling isn't, the bird is superior there. Get the R3 if power and speed are more important to you than anything else, otherwise get the Tbird.
I will say one last thing....there is something very special about this bike that you really can't put your finger on. But it's a special machine that just makes you feel like everything is so in balance, and i think everyone here will agree.