I have always understood 3D to be flying in a stalled state--not on the wing or high speed KE like conventional flight. This puts the plane in a High Alpha attitude as it is flying on vectored thrust. (Elevators are stalled & HE for the path of the plane)

Most planes that are powered correctly can hover. Does that make them 3D? Yes, that means they can do a 3D maneuver. Does that mean they are a good 3D plane? No.

By some peoples definition 3D is suppose to seemingly "Defy the laws of Physics". ( I think from the Ultimate 3D dvd http://www.jpmediainc.net/ultimate3d.html )
This means that the plane has to look scale before it can really be considered good 3D.

I like my 3D planes to look scale and be IMAC legal. I like them to be able to fly IMAC a sequence precise, but still be able to fly nicely in a 3D stalled state--to be capable of flying a Freestyle routine. Why? Probably no reason other than vanity. Beauty lies in the eye of the beholder I guess.