They all have the same mileage and cost the same!

I don't think Infiniti is quite in the same class as Lexus or Acura (and I -own- an Infiniti and that's why I say that). Among the two that are left, I'd say the Acura is probably sportier and better-handling and the Lexus is probably more luxurious and more comfortable. They are both great cars though and you'd probably be happy with either one. And the Infiniti, while not in the same class, is still a pretty good car.

I'm not sure how this question is related to "TRAVEL". It seems to be one that would be better suited to the "CARS & TRANSPORTATION" category.