Melissa is right, I'm a stylist and i would say go with a U. It is a pretty cut. A V cut is kinda out of style now. But to actually see a V shape their has to big a big difference in length from the shortest part to the longest. And you only have your length in the back which just doesn't make since to me. If you have long hair show it. A U will give the length a have some movement in length in the front. If you really like a V cut try going with a U first, Seeing how you like it then go for the V. Cause if you don't like the V you have to wait for it to grow out.
I have thick long hair and you can honestly do either one. My hair stylist said a U is more flattering though. I think a V is good is you have long layers