I'm not very familiar with gas engines but to give you a better perspective, the OS 1.20(non pump) was actually ok. It didn't have insane vertical power but it was plenty enough to do what it was supposed to, fly scale and do pretty much everything.
If I were to get another one, I would definately go with the YS 1.10 for the light weight and power.
The thing you need to watch out with these Gee Bee's is the weight. I understand there's quite a significant weight increase with gas.
I think that's the only thing you need to watch out for.
I kept mine under 5 kgs, about 11 pounds.
If you check some of the earlier posts, there was a guy running gas, he said it was great but a bit on the heavy side and it sorta dropped out of the air during his approach...