I prefer belt over shaft because of many reason's when it comes to high powered engine's twin engine, high powered single or brushless or etc, one problem of shaft drive is this
http://www3.towerhobbies.com/cgi-bin...?&I=LXJBM3&P=Z
Many of these have went out to soon on the GTX2, and other shaft driven Rc's I've had. This is to say without full throttling it. There is just too much power being put on this part for it so easily to go out. With belt drivetrain I dont have to worry about this particular part failing. A belt can last a lot longer than a bevel/spiral gear.
Elven Wizard