Ringed engines have more friction when running than ABC/N engines. Believe me on this one. Take the OS .40 FSR. They made two versions, a ringed version and an ABC version. They were identical except for the pison and liner. The ABC engine was more expensive but put out more RPM.

In your case, there are more differences between those two engines than you think there are. They don't appear to share the same crankshaft or connecting rod. For your statement to be the same, the stroke of both engines would be the same, the .50 would just have a larger bore. In fact, the .50 has a stroke of .847in compared to just .770 for the .46. I looked at the parts listings and specs on www.osengines.com

On the other hand, the .40FX and .46FX ARE the same engine with just a larger bore on the .46, both have a stroke of .770, but the .46 has a .06in larger bore (.810 vs .870)

So comparing the .46 and the .50 is a non-starter, they're way to different.

whstlngdeath is right on in his description.