AAU IO has special requirements on all events which are worth .2 (USAG L7 special requirements are worth .5).
IO requires 1 B skill and L7 requires 2 B skills. Both require 5 A elements.
Vault values differ, at L7 all counting vaults are worth a 10, IO has different SVs for vaults, and I believe a Front Handspring vault is worth a 9.4, I think. I don't have it all in front of me right now...but it is definitely NOT worth a 10 like it is in L7.
AAU IO Special Requirements:
UB: The only special requirement is a bar change...significantly easier than L7
BB: Full Turn, Dance Connection, Acro Skill (no flight required) & a dismount with flight (with or without hands)
(EX. Routine: Full Turn, Split Jump/Straight Jump connection, Cartwheel, Wolf Jump, Front tuck dismount)
FX: Full turn, leap series, 2 tumbling passes (containing at least 1 flight skill)
(EX. Routine: Full Turn, Leap/Side Leap connection, FHS Step Out/Round-off, Round-off Back Tuck)
AAU IO is more similar to Prep Op than L7...however, the biggest difference between IO and Prep Op is that in IO non value-part skills that are in the compulsory routines DO NOT COUNT. So, you can't do a 3/4 handstand on beam and get credit for it.
Lots of gyms that compete AAU use IO as a transition between L5 and L7 if they don't choose to compete L6.
We judge a TON of AAU in our area, so let me know if you have any additional questions.
Hope this helps!