Just to break it down for you some:
TF2 - Much more arcade-like in feel. Not to say there's no teamwork involved, but it's very fast-paced as far as FPS goes, akin to Unreal Tournament. Lots of explosions, limbs flying about, and hats. If you are looking for something different than CS:S, this is your choice, however, you will be thrown off by the tempo difference.
DOD:S - It's similar to CS:S in the fact that you really can't go in guns-a-blazing and expect to do much. It's much more tactical in feel than TF2. You'd fit in rather decently coming from CS:S if you go the DOD:S route.
I own both games, and personally I like TF2 better, mainly because I grew up playing alot of fast-paced FPS shooters like Quake, Unreal, and Doom back in the day.