While I am not responding for rcign, you will get more power out of a good used engine than a new one. (at least until the new one is broken in) most people go with the new ones because of weight. The older engines usually weigh more unless they have been modified by someone who knows what they are doing. (rcign)

A G62 from rcign is as strong as some of the newer 50 and 60 cc engines and about the same weight. While I am not an expert, the piston and cylinder is about the same for most of the engines, the crank and case may be different.