I was between the YS110 and the OS120 two stroke, and I went with the OS and I'm glad I did. I was told that the YS can be tricky to get setup and running right, and without any kind of guidance it would be a bit of a gamble.

What it boils down to, and also what I was told, is that us beginning pattern pilots need to be concentrating on flying planes and not tuning engines. There is plenty of time down the road for getting into fancier setups, but right now it's all about stick time.

The OS two stroke has been awesome - gobs of power, and yes, cheaper fuel (10% nitro is $35/gallon here, the high nitro fuel for the YS is probably $50).

I suggest getting the engine set up without the pump and the tank at the firewall, and once the engine is dialed in move the tank and install the pump. I didn't do it this way and struggled to get everything running right. Beginners need less variables, and this is the way to do it. I've since pulled the pump and am just about happy with the engine and will be putting the pump back in and the tank back to the CG (probably over the winter for first flight next season).

Keep it simple
And go BIG