Yes, EFF is a simple raw good minus bad calculation. PER is adjusted for minutes played and pace. When comparing rookies, I definitely prefer EFF as it accurately reflects actual production. If you use PER, some guy who scores a couple meaningless baskets during garbage time once a week can have a higher PER than someone like Lillard who is starting, playing big minutes every night, and making a solid contribution to his team's success.
For example, if you
sort the current rookie class by PER, 6 of the top 10 have played 62 minutes or less. The top two are Diante Garrett and Scott Mchado at PER = 42.1. They've played a combined 8 minutes all season and scored a combined total of 4 points.
So, for comparing rookies, I'll go with actual production over minute adjusted, pace adjusted garbage time stat padders any day.
PER is more sophisticated, but it's best used for comparing players of similar roles.
BNM