Tough decision. Not sure how prep-op works as it isn't an option here. If the girls practice the same hours and eventually get tracked back to USAG optionals successfully, then I would probably consider it. I know my DD would much rather get her own routines and show off those uptrained skills she has than do level 4 again. LOL.
My questions would be:
1. If she does prep-op, when will she transfer back to USAG and how does that work? How do the girls do at the gym that go straight USAG compared to those that go the prep-op route? Do they devote as much time to getting good solid skills to the girls doing prep-op as they do for USAG girls? Are they in same or different training groups? Are hours decreased? Do they sacrifice form, solid skills for fun?
2. If she repeats level 4, will she be uptraining for level 5/6 skills to keep her challenged? Do they do move ups mid year or will be be in the level 4 group for the next full year?
My DD is repeating level 4. She wasn't excelling at level 4, so it is the best thing for her. Her new gym uptrains and does progressions for L5/6 skills even now that they are also working the routines for meet season that starts next month. She has her kip, squat on and jump to high bar and long hang kip, working on FHSs, flysprings (prep for layouts), front and back tucks, etc. I worried she would be bored doing level 4 again, but at her new gym, she is loving it and is looking forward to having a good solid, hopefully confidence boosting level 4 season.
If the prep-op program is just as solid as the USAG program, it sounds like it would be a lot of fun. I wish they had something here besides USAG sometimes. Not sure my kid will make it out of compulsories and it would be nice to have some options so she could taste having her own routines, show off her strengths, etc.
Good luck making your decision!