Check out this post from Martin Fowler. The sample size is 99 responses, but look at what tops the list. Look at the contrast between Clearcase and Subversion.
Subversion’s only downside is repository replication across different sites, a reality for our business where we have teams around the world working on the same code base, and the code base is BIG, so downloading the “whole ball of code” from a remote server just won’t work efficiently. The only solution I have come across so far is WAN Disco’s multisite solution. There is a video here describing it. I have never used it and would love some feedback from anyone who has experience with this solution.
Lots of good stuff on Martin’s blog. Including more details on the pros and cons of different source code repository tools.