Less players on HC Modes, but I will tell you this. You find more competitive matches on HC than core and it has nothing to do w the fast ttk, it's just full of better overall players.
Core has more players, which most times lead to a bunch of newer players on a team, it's ok when you're playing against them but when those players are on your team it's a loss, unless you're pulling out 30- 10 or higher.
HC has less players but you get better balanced teams imo.