Hmmmmm?  The O.S. of gas engines?  Heavy and expensive for it's power and prone to cylinder delamination.  Hmmmmm?

Seriously, Zenoah is rugged and dependable.  I have two Fujis that I like and have had very good luck with but have heard complaints.  Syssa is (I believe) American made and I would throw business that way just because.  Desert Aircraft are light, nice and priced accordingly.  Same with 3W.

The latter two if you want a serious 3-D model.