Hendo was a smoother athlete and more natural in coverage. Horn is stiffer and plays a step slower, Pro Day times be dammed. He's also more reactive, whereas Henderson would run the route for his man.
Where they are polar opposites is in physicality. Hendo had a horrific missed tackle rate and wanted nothing to do with contact, whereas to borrow from PFF, "Horn plays every snap like the receiver just personally insulted his family." If Henderson is Deion, Horn is Lester Hayes.
I had zero doubts about Henderson's coverage skill translating to the pros, but his total aversion to hitting made me wonder about his mentality. Is he soft, is he a Deion-style prima donna, does he even like the sport of football or is he a track guy just playing CB for the money. We've seen how many talented guys bust because their head wasn't in the game, and after watching Hendo ole like 5 runs every game, I thought it was fair to question if his was.
No question that Horn loves football and is out there to straight-up ball, but his overaggression scares me. Looking at recent top CBs, Henderson played very under control in coverage. Surtain plays extremely under control. Okudah played extremely under control. Horn OTOH is biting on everything to try and make a play. If you are projecting Horn to play CB1 and line up against the top 20 WRs in the league, all of those guys run routes well enough to bait him time and again. He'd get destroyed right now by Amari Cooper.
Just on tape, I'd say Henderson was clearly better, and my only questions with him were off-the-field motivation stuff that we fans know nothing about.