While I realize it is too late, I see you are in NY. I don't think you will "regret" getting the 19s when you hit a pothole. Alas, the 20s do look good. Even though I don't really like the look of the style 336 wheels, a friend of mine has my exact same X6 but with running boards and 20s and um, well I hate to admit it, it looks a lot better. I still don't regret the running boards (my 5' 3" wife sure does however), but sometimes I think the X6 would have a lot more pop with the 20s". And then I hit that next pothole and I'm back to being grateful for the 19s
PS - it hugs the road just fine with the 19s