RE: Which Gasser
Just to narrow the playing field in the price bracket you may be interested in, I would consider the Aerovate/RCGF, the DL, and the XYZ. DL has the longest current type history, mostly good. The Aerovate engines are working out rather well. I have 2 of their 100cc engines and am generally pleased with them. A good friend, Al Lewis, has been testing the XYZ and is happy with it so far.
So price and weight will likely be your final considerations, but parts availability should also factor high. At the moment DL seems to hold the lead in that area.