As I see it the DM can always win if he really wants to. The players need a at least a chance to win, games where the PCs always lose tend to fall apart.
So in groups that work, the PCs need to succeed at least part of the time. It's just a question of where the DM draws the line on what works and what doesn't.
I prefer combat as sport as a player and a DM because it's less stressful for me. DM's vary amazingly on what they consider valid tactics and strategy and what they don't in a combat is war style and figuring out what's what can be a painful process, and one I don't find fun. There is no guarantee that what emerges as effective tactics in CAW will be fun, interesting, or acceptable or believable from a particular PC, especially as I tend to play heroic PCs with moral qualms.
I think Combat as Sport is easier for new players and casual players. Combat as war needs lots of investment and preparation on the part of both players and referee, and misunderstandings and different interpretations can make the style backfire badly.