If you consider 'high levels' as the more endgame levels, the hunting grounds become mostly similar. So to your question, I believe it depends a lot on your playstyle.
I feel the major difference is whether you prefer hunting solo or with a team. RP is more flexible when hunting solo, using diamonds+AOE runes+caldera to defeat stronger hordes of monsters for more loot. EK will do better blocking for a team, which means the loot is divided but with higher chances of very rare and profitable loot.