Not a great fan of either, Hayes is slightly ahead on my WS/faux EWA pythagorean ranking. However with a low, (sub replacement level) baseline for WS Hayes' edge might be somewhat artificial. Iverson whilst he doesn't blow you away is better on my equivalent for peaks coming in at 105th
where as I've said Hayes doesn't make it onto the board.
I'm not convinced by either as a centerpiece to build around. Some similarities in their flaws (volume scorers on below average efficiency, though Iverson shouldered a larger burden and I think was closer to league norms, both with abrasive personalities or some personality issues). I'm not entirely convinced Iverson's best asset (shot creation) is that valuable on better teams (because of inefficiencies), but then I'm not wholly convinced Hayes had such a huge impact either (generally pedestrian per minute metrics, the only thing in his favour is big minutes, which if you're not great doesn't mean that much, WoWY/impact type stuff, in which there might be too many moving parts and player development to isolate Hayes' impact). Fwiw both share positives too (seeming to work hard on court, big minutes).
I presently lean AI, but am not sure if I'm doing so to get him out of the way, plus I'm not confident on Hayes' impact, maybe as has been suggested he was having a large defensive impact though only two 2nd teams over his long career with those forward spots, I would suggest, quite open (at least later, and on the 2nd team, at first DeBusschere and Havlicek, but they and Silas age/retire only Bobby Jones really comes in and there are a lot of historical non-notables making Defensive 2nd team as forward) gives me pause. Not that such accolades are perfect. Maybe his reputation preceded him. The Hollander handbooks don't give the impression that he was the clear leader in defensive impact, noting Chenier and Riordan as much as Hayes, later Dandridge comes in with a good rep at that end.
As I said, leaning AI, but not confident enough to vote either way.