You'll get many opinions on this.
What I've heard from both prepsters & non that appears to be holding true is:
1) Prepster plebes have a distinct advantage having had a year to get their military routine dialed in. Including time mgt, etc. How to efficiently get stuff done. Add to that the prior enlisted aspect of some, and it's a big difference initially.
2) Being less challenged by the mil stuff & duties, prepsters early on are often able to handle plebe academic loads without drama, etc
3) The early advantages start changing as yearlings. Mil duties are lower, cadets figure it out, etc. AND academic courses get much harder, physics, etc. It hits all cadets, but there does appear to be a greater impact on prepsters, just due to the nature of their background. Many dig in, get tutoring, and tough it out. Others struggle.
Tutoring apparently becomes a big deal in the yearling world. Help your buddies, and get performance passes to boot!
All of this is a generalization, there are exceptions to every case. But there do seem to be some trends that appear.
Regarding class officer positions, etc, even the prepsters will admit there is no competition early on. They exit USMAPS with essentially a voting block, focused distribution lists, parallel information flow. Some share this info with squaddies, others do not. There is virtually no way for non-prepster class officers candidates in BEAST to challenge that level of organization. I'm told that it's very rare to have plebe class officers who were not prepsters, if it happens at all.
One thing for sure- having a prepster as roommate as a plebe is a big win! Much to learn from them.