Aimee isn't a trendy version of Amy, it has been used pretty frequently over the years.
I don't like Amy or Aimee, the name is just so bland and blah, like Sarah or Mary. But if I was going to use it I would use Amy, I have a friend named Aimee who is in her thirties and she has always had to spell and respell her name; plus there are so many other Amys and Aimees her age that it was doubly hard for her to keep people straight on how her name was spelled.