IIRC, the new style has 5 slots, whereas the older had four.  Supposedly this makes it more effective.
I've yet to see a head-to-head test of the various AR flash suppressors, but I sure would like to.
Because of the new configuration, I'm not sure if the new Phantom can be modified with wire-cutter cut-outs, such as the old design had.

Various FS units:

3-prong:  The original, and more effective than the A1 or A2.  Snagged on brush due to open end.
A1:  Worked well, snagproof.
A2: Worked pretty well, snagproof, and closed bottom acted a little as a compensator and lessened dust kicked up by muzzle-blast. Only FS that must be properly aligned to function as designed.
Vortex:  Most effective of all, but shared the drawbacks of the old 3-prong.
Phantom:  1st version reputedly as good, maybe better than Vortex.  Snagproof, with wire-cutter capability.
Phantom: 2nd version: reputedly more effective than version 1, but wire-cutter capability lost.  Snagproof.

Balancing all the above, I think I'd select an A2 for almost all applications.  If I were going to be operating a lot with NVDs, I'd look into the Vortex and Phantom II.  In that instance I'd select the Phantom II if it and the Vortex were equal in suppression capability. YMMV.