If Budget is no object. The Extreme Flight 50CC Edge 540. It is a beast, also you can upgrade the motor up to a DA 70. It was designed for the DA50, the 55 will give it a little more stuff.
Here is RJ Gridder at the King 50 finals
[video=youtube_share;RKz88vcOx00]http://youtu.be/RKz88vcOx00[/video]
Here is Jase Dussia and Ben Batts flying the same plane with the bigger motors
[video=youtube_share;R1_xxZ4W9kg]http://youtu.be/R1_xxZ4W9kg[/video]
I almost bought this plane, but the budget was an issue for me. However it's an incredible plane in every way. Flys locked in, and balls up extremely well. If the top guys need to to Precision Aerobatics, they often choose the Extra 300 (the EF 104 is at the top these days).
If you look at the last few years of major competitions where 3D is judged with equal footing with pattern. Extreme Flight and 3DHS is mostly at the top, then you see PAU & Aeroworks (maybe even a H9) sprinkled in.
I just went through a similar search for the best 3D monster, but for a DA-50. The problem is, when you look at these top air frames, a 50CC as become 60-70cc. That is to say the current offerings that used to use a 50CC motor, are a little endemic due to the new larger air-frame size offerings.
I ended up gong with a little smaller of an air-frame for my motor size. Knowing that I will have to pay close attention to throttle management so I do not over power and break the air-frame.
Not many will argue that EF, 3DHS, and PAU are at the top of the game. However there are some exciting new stuff that's making it's way up. AeroPlus RC, RedWing, Even Pilot RC is trying hard to be the best. Often times when buying an air-frame, it boils down to Customer service, and added costs such as shipping. I say this because most of them fly so well.
What makes a great 3D/XA plane is different than what makes a great I-MAC plane, this is why I left out companies like Comp-Arf, Krill,ect.... In the end everyone has an opinion, and I am no different. I just wanted to share with you what I believe after many hours of research, and talking to some of the best RC pilots in the country. With all that said, you don't always have to buy the best to get a great flying airplane. I cant say enough about setup. Even a cheap air frame, one that's set up well, can be locked in, and can do everything the rest can do when in the right hands. In the end, all we can do is try to utilize all available information, to make the best decision we can.
Good luck with your search, be sure to tell us what you decide, then be sure to do a build thread so we know what you have going on. AKf