Did you ask this at another forum? because i answered this somewhere else recently. Anyways, i don't know if you will or not, as i'm not you. But i can give you my thoughts on the difference. The Vrod is a higher tuned engine. It's a little further towards a standard bike rather than a cruiser which is more of a low RPM torque machine. Thats the big engine difference as far as performance. The rod is going to be quicker but the Tbird will have more low RPM grunt and may take the rad thru a couple gears or so. Then it will watch the rod go by. You have to weight whether thats important to you and what you're willing to trade that for. The Tbird will outhandle the rod with ease. It's probably the best handling cruiser ever built. It's smooth and comfortable, handles like mad and has a lot of torque like i said.
You can take that info and weigh the differences and see what you come up with. But unless you ride one you'll never come close to having a good idea as to whether selling the HD and getting a Tbird is what will make you happy. To me it's easily the best bike i've ever owned or ridden. But again, i'm not you. Demo one asap. Make it a 1700....the 1600 is rather weak due to the cams in the 170-0 being much hotter.