I play everything on random at Immortal, so for me, it really depends on map type and what VC I go for. For me warmongering is always my best bet of winning - I guess I have a 95% win rate if I warmonger (if it's an ocean map = 100%). Recently I've tried to limit myself to peaceful wins on a Large Pangae map - that makes it a lot harder for me, and I drop to 50-ish %.