A 660 is probably the best saw ever made,numbers sold and still running and reliability have to put it close if not the top saw.
A 044 is just as good but the logging industry has made the 660 what it was.
A 661 in 10 years will have the same reputation,there excellent saws.
I've ported several 12mm saws and only one 10mm and the 10mm is a good bit ahead for no other reason than it just is.
I don't know enough about them but flywheel weight and better timing has a lot to do with it