The Hacker A10-15S has a great reputation in the F3P competition scene, is a very dependable and powerful motor. I even use them on many of my lighter freestyle planes.
They weigh about 14g, and can be taped on with the provided mounts
, which saves a few more grams.
Mine have taken a beating, and keep on going. They will cost about $6 more, but are well worth the extra cost.
Here is where I get mine,: http://www.aero-model.com/Hacker-Brushless-A10-15S.aspx