If your looking for an engine to fly one of the larger scale type planes, a US41 is fine, if your looking for an engine to fly a "performance" type plane look elsewhere. Here are the facts, I own both.

Brison 2.4

All up flying weight - including battery ............... 3 lbs. 8 ozs.
RPM with an 18-10 MA Classic prop ............................ 8000

Q42 (same as but better IMHO than US41)

All up flying weight - including spring starter ............. 4 lbs. 8 ozs.
RPM with an 18-10 MA Classic prop ............................. 6900

My Brison has been in contant use for 7 years.

My Q42 has been sitting on a shelf for 11 years waiting for the "right" plane, maybe it never will.

It all depends on what kind of plane you want to fly, 1 lb. less weight and 1000 more rpm's is a HUGE difference.