My results bear out BigEdMustafa's. I've owned two TT Pro-46 and have been very happy with them. I have a Perry Carb on one and it has a narrow but noticable "sweet spot" for high idle but the broad low idle range was worth the "upgrade". Not really an upgrade, but a dirt nap destroyed my original TT needle valve and a new carb housing from TT was 3X a Perry Carb.

My OS 40 LA is reliable but a snoozer in comparison, and my Super Tigre G-51 is noticably stronger than the TT Pro-46 but requires a bit of work to tune it to changing conditions.

I haven't tried the newer OS AX series to see if they are as nice as the older FX models. The GMS engines are more prevelant locally than the Tower, but I've never flown or been exposed directly to either. The GMS seems to be a solid enough egine and there are several in my club that like them. I have yet to see an Evolution engine locally/in person.