I'll add my wife has the smaller Ogio Endurance 7.0.
Both bags have external helmet strap systems, which are nice. But the 9.0 is large enough I can fit shoes, clothes, track sack, towel and helmet inside the main compartment. The helmet strap would let me bring two helmets - regular and aero. It also has two external pockets for bottles (7.0 has one).
There are also plenty of pockets on the side and an expandable area for storing a wet suit - would probably work for a track sack as well.