I have flown with plenty of guys in the right seat that have come straight from ab-inito to jets & also with plenty of guys who did lots of GA before coming onto jets. I rarely see any big difference, in fact if I would make a guess I would say that the ab-initio guys were better, but that's just my personal opinion. Whereas the guys who come GA have lots of experience that are also prone to having extremely bad habits & tend not to work well in a 2 crew enviroment. On the other hand the AB guys tend to be on the timid side & rarely attempt any decision making. So it's 6 of 1 & half a dozen of the other.