By far...field games. As long as the field is large enough and not barren, there's infinite possibilities and permutations.
Unless the cqb facility is huge (ie picton, where rhino is this year, pine plains, etc) or unless it's designed to be different every time (ie TTAC)....cqb places get stale very quickly. It's like playing the same level of a video game over and over. That has it's place for training and team building, but I tire of it for repeated game play.
I'd lump flag raiders somewhere in between. If it's skirmishing on 1 section of the field...it gets boring very quickly. If it's opened up to a couple of fields or the whole place then it's a completely different environment. Even with the same structures, roads, hills, etc...if it's opened up it's a good mix of everything.
Comes down to what you're looking for...who you're playing with...and how it's approached. As long as everyone's on the same page it's all good...skirmish, milsim or something in between.