Thats a good question Chris, In my own opinion formed from running both for a long time I would have to say that Given the 120SC is a deal heaver and also you must run 550" wing not to mention the cost and maintinance is much higher, I will give the nod to the 115. Actually I flew a YS91 powered plane as a back up in the last race that when flying wide and backing down to only a 12X12 APC it's a breakout fool....Go figure??? I believe small and light is always faster, But what do I know..LOL

Dave