TFS for large scale enterprise, hands-down. But I don't recommend it for small shops. (Expensive, although I know it's free for shops with 5 devs or fewer) simply because code management is easy and you can build automated deployment without having to use anything else (you can script with PowerBuilder, Ant, whatever if you like, though). The issue I've found with that is it's not easy to find people who don't code for a living but understand scripting enough to build automated deployments. I'm also not crazy about TFS' visual displays of branches - ClearCase (which is god-awful in every other way) has the best visual display of code and branches.

Mercurial for anything smaller or startup. Love it. The issue with Mercurial is that you'll need to determine how you want to do automated deploy builds, but the code management is great and using BitBucket + Hg I never have trouble seeing which code I'm working in or resolving conflicts. I actually think Mercurial has the second-best visual branching display.