martinoto,

YS63 is in a class of its own.. As Don M said, no engine will match the transition speed and upline torque of a YS.
Also I saw with my own eyes the YS63 on 20% nitro turned a 13x6 APC at over 11400 on second tank. thats more than 1000 RPM than 56FSa or 70 Surpass.

YS63 with 20% nitro and 12x8 or 11x10 is a very frightening pattern power plant.

YS63 on 20% nitro is about as powerful as an theoretical saito 85 or something.
Its power is just shy of 91 surpass and probably in the same neighbourhood of 81FSa.

I'd go for YS power and transition on a pattern ship, if I could afford the 20% nitro fuel. In alternative Im going for 2 stroke power with tuned pipe with 5-10% nitro.