Lots of guys are going to the new small gassers for economics; they're a BUNCH cheaper than say a new YS engine. Then there's the fact that YS engines just LOVE 30% nitro fuel which around here is near $40.00 a gallon and a little YS-110/115 will go through about an ounce a minute of that fuel.
There are a couple of the older Funtana 90's around here with the little 26cc gassers and they fly okay but neither of them will keep up with my Funtana 90 with a YS-110 on the nose, but they cost those guys a lot less money to buy and operate and the little gas engines are a lot easier to tune. Downside is they don't put out the power a YS will and they are heavier.
Your choice but the small gassers seem to be the way most folks are going and I would not put a 20cc gasser on a 25% size model, you'll need more....
OH.... Edge or Extra?????
I have both and like both but you need to pay attention more to the manufacturer's reputation and reports of how the models fly as the same model from different manufacturers can fly very differently. I'll repeat something my IMAC mentor told me when I was trying to decide the Yak/Extra/Edge question; "buy the one you like 'cause you'll fly one you like more than one you don't like and practice is much more important than which airframe you fly...."