UCD would be a mistake. Good to learn to hover, bad for anything else 3D. I have not flown a Flip but I have heard good things about its 3D abilities and I have seen videos of the Flip doing good 3D. Do a search.

If you decide to look beyond these 2 airplanes, the Funtana 100X would be a good choice. I've seen many fly at my field and have heard good things from the guys locally who fly 3D. The easiest choice for learning 3D is a profile. Get a couple of them and fly the heck out of them. If you crash one, fly your backup and then fix the damaged one. Who cares what a profile looks like - you said you wanted to learn 3D right? Once you get the moves down, you'll be able to do them on a nice looking giant Extra, Edge etc.