hey guys, what are the differences between a 353 and a 12-3SCT?

obviously the extra $$ is for the extra motor you recieve in the package, and the 353 is a newer engine, but is it actually better then the 12-3SCT??

i've read different reviews that some say the 353 has a 11.9mm and others say a 11.5mm diameter...

The only other difference i could find were the extra holes in the 353 sleeve

Tossing up spending $390US for a 12-3SCT or $529US for a 353