I ride the GNU Mutants. I wanted a quick entry binding last year to keep up with my skier fiance.
Last years Flow's did not have the toe cap. I found the toe cap on the GNU gave me better torsional flex control in the store. The lack of toe cap seemed to hurt the torsional flex control of the Flow's compared to the GNU's.
The GNU's were also easier to get into. This was due to the auto tension release on the ankle strap when the high back was brought back. The Flow's did not have this and it made entry harder.
I think both items have been fixed with the new generation of Flow's. The differences in the bindings at equal stiffness ratings and equal costs are probably minimal. Just make sure you try one of them before you buy it.