HoH vs KC5 (vs Twilight Perion)

What Thorr said.
HoH's layout is better.

The mobs at HoH only spawn on two platforms, so it's very easy to cycle. The bottom and the ladders leading from it to the first platform are safe, for leeches and mules. Kanna can stand on the bottom to recast Kishin conveniently and safely. HoH's only real drawback is the mix of enemies, some of which die before the others or respond differently to certain skills.
The safe spots in KC5 require more precision in positioning (I'm not even sure they're safe under all conditions). The split platforms make cycling difficult for classes that can't easily leap the gap, or can get knocked back and down, and also force you to fight smaller groupings of monsters.
I don't know the Perion maps yet.

I think that this is the sort of thing you just need to try for yourself. We have many, many hours to grind. Might as well do a couple of hours in each map, and see which one gives you the best exp with the least headache.

i'd say HoH too, i tried finding a safe spot on KC5 ages ago, i just couldn't, their soul wave has enough vertical range up and down to hit you anywhere, and even with impale's long reach, i was hitting less mobs than in HoH.

maybe if i had perfect connection to OHKO everything with dark synthesis every 8 seconds, then maybe KC5 would be better.