We are a mostly MS shop at work doing .NET LOB development. We also use MS Dynamics for our CRM app... all the devs are currently using VS/SQL Server 2008. We also use VSS, but
The old TFS Build was XAML based and very cumbersome and and not nice to work with. That said, the new TFS 2015 build system is leaps and bounds better, and is script based with lots of web hooks and 3rd party integrations; very similar to Team City. Also, TFS now supports Git, so you are no longer confined to using Team Foundation Version Control (TFVC). Also, with TFS you can use your own on-prem installation, or can take advantage of a hosted solution through visualstudio.com. TFS is great because it's one completely integrated environment (work items, planning, builds, tests, deployments), whereas Team City is just a build solution. When this question was originally asked in 2010 I would've recommended Team City hands down. Now though, the 2 are very competitive. I would say that it would maybe boil down to if you want an all-in-one solution, then go with TFS, but if you are looking for purely just a build system, then Team City.