I would say Gears of War, just because I've come to prefer cover based TPS over FPS titles. That, and the fact that I've actually finished the first 3 Gears titles, but haven't finished a single Halo besides Halo 3.

Gears of War.

Halo. Prefer the speed and movement of halo, prefer the locations, prefer the skillset, the gameplay diversity with vehicles etc, the more open areas, the high sci fi setting, the music, the art, the player options (building your spartan).

The heart of it for me is the local multiplayer, thats what got me into Halo.

I played the first Halo in PC and finished Gears in the 360 and started the second one was well.

Gears has a nice campaign but storyline is a little lacking. It is pretty much about guys talking about tactics and what they need to do and some sarcastic comment here and there. It feels similar to Killzone but without the interesting enemies that Killzone at least has.

I played Gears after playing Uncharted so I kind felt like I was heavy and stuck to the floor without the ability to traverse territory and go to higher grounds and stuff.

Halo Combat Evolve I mainly played the multiplayer but I also started the campaign. It feels like a paintball mash-up with a rave party with all the colors and lights and shit. I must have put over 50 hours in multiplayer messing with the guys at Uni.

I would call it a draw or something. To me both games are like 7 or 8/10.