If you're talking 3D flying, at 12.5 the OS will be at the upper weight limit. The Moki will pull 12.5 lbs around just fine. Anywhere near the 14 lbs and you better get the Moki 2.1. The OS 160 will only be good for sport flying at 14 lbs.

Moki 2.1 46 ounces
Moki 1.8 41 ounces
OS 160 33 ounces