While the LLVM compiler infrastructure is primarily developed around Subversion, a poll was recently conducted that found LLVM developers overwhelmingly prefer Git over SVN for version control.
The poll only occurred for a few days and was done in a rather hasty fashion, but the results of SVN vs. Git for LLVM can be found on the llvmdev mailing list
. A majority support Git-only, a small number support SVN-only, and then an equally small number support having both forms of version control. It's about a 3-to-1 favor for Git.
While the LLVM Subversion repository is what most often is promoted, there is a Git mirror for staying up-to-date with the latest LLVM code commits along with Clang and other compiler components. GCC compiler development also continues to be heavily SVN-based.
Speaking of polls, be sure to participate in the 2012 GNOME User Survey