I assume you meant to ask me this?
It isn't so much about what Helix can or can't do. Helix FX are very good and the control center makes running the H9 very easy. It's about getting more out both devices. Using the H9's offloads some DSP power away from Helix and therefor allows for more amps, IRs, and routing options. The H9s do have a greater number of available effect types. Plus, the reverbs have better detail than the Helix reverbs. The H9 also has MIDI clock sync. Helix doesn't yet. OTOH, Helix loops can be inserted anywhere I want the H9 to be. And, I can used the expression pedals to control the H9.
Helix and the H9 is serious powerful combo. Really, I'm just scratching the surface.