there seems to be a three way tie at the moment between OS 46AX, Evo 46NT and Thunder Tiger Pro46.
Reliability and performance out of these three are nearly identical.
Cost is an issue. OS has a rear needle but cost alot more.
Some people will buy OS simply on the name.
Evolution is the new kid on the block and so far reports have been positive.
Thunder Tiger has been around for a while and although there were quality issues in the past that seems to not be the case any more and the Pro series of engines are great performers.