If you put avgas in your IT125 then the advantages would be pinging less and taking longer to wear out and that,s all , waste of money really.
If you were to put it in your 86/ 240 CR husky [ compression ratio 15/1] then you could expect a small hp rise and less pinging and it would take longer to wear out. You could also advance your timing giving more hp but kicking back and breaking foot/sidecase/kickstart bits.
The moral to my story is that avgas is good but you have to design your motor to take advantage of it's good points.
I still don't understand how you can use a fuel with less BTU's and get more out of it but that's another argument.
Cheers