I own a Sig SE and a .40 size GP Extra-300 and there is little comparison for 3D. - The SE is head and shoulders a better ship for that:

My SE has a Saito .72 and a 100% larger rudder just for 3D hovering and knife edge. You will need a strong, light motor such as that or say a K & B (gold head) .48 for comfortable hovering power (even though you will spend the rest of the time around 1/3 throttle). The rudder enlargement is needed since the stock rudder is inadequate for holding a vertical hover. - But it's an easy fix and works great! The SE is intended to be a s-l-o-w flyer and it's thick wing will not build up speed as fast when you point the nose down which is just what you want for 3D. It still won't do a knife edge loop, but the larger rudder will give you unlimited straight and level knife edge flight. The throws and GC variations can set it up as a gentle 2nd plane or a wild and woolly beast with just a flick of the dual rate switch on your TX.

My Extra-300 is a .40 size with a Saito .91 and is still difficult to hover due to the size of the surfaces and the plane's small size (bigger is way easier to 3D) It will fly a great scale aerobatic pattern and will track and knife edge like an SE won't, but it is really intended for a conventional flight envelope and not the 'fun fly' style of maneuvers you want to do.

Bottom line seems to be that the SE can fly 3D in a compact size package and an Extra-300 won't match it until you go to the 1/4 scale and larger ships. The Extra-300 is so smooth and tracks so well when doing big maneuvers and the SE will seem to float right in front of you as if it was hanging on a string. Both are a blast in their own environment. Just 2¢ worth.

quint