I have been racing 1/12 scale for a while and have tried a few motors. The DUO/DUO 2 would be my vote. I have personally ran the older Novak, the Orion 2008, the Hacker e40 and currently I am using a Fantom Ion 2 (Duo 2).
The Novak motors are great and I would like to try one of the newer Ballistic motors. Great top end, bottom to mid power was ok, very forgiving with gearing.
The Orion motor just felt slow all the time and it could have just been the one that I got, but it had ok top end and poor low end. Probably my least favorite motor that I have tried.
The Hacker has great bottom end, but it was hard to get the top end out of it like I had with the Novak. Just have to gear the Hacker a little higher than the other motors. With it being geared a little higher it tended to get a little warmer than the other motors and faded a little around 6 or 7 minutes.
Finally the Duo 2... best of all worlds. As much low end as any of the other motors, great drive out of corners, stays cool no fade and top end is great. The fastest cars at the tracks I race at are using the Duo/Duo 2 motors.