I always have played control plainly because I felt that the other game modes were too easy. This assumption wasn't exactly based on first hand experience, rather it was based on people almost always having higher k/d ratios in Clash, Salvage, Rumble and Skirmish. I decided to give these game modes their fair shot on my warlock to see if my assumptions warranted. I can now say, with full confidence, that the game mode that presents the most challenge is Control, so those who run around with 2.0+ k/ds in those game modes and think they are exceptionally good at destiny, please test yourself in control first, as it will probably be a vastly different experience.