From a quick search, Linux kernel is ~40 million loc, freebsd ~9 million, openbsd ~3 million. Number of bugs compared to lines of code leaves FreeBSD looking worse than Linux.
I assume those are lines of code in just the kernels.
As an FYI to everyone: The OpenBSD and FreeBSD teams both maintain entire distributions, similar to Linux + Debian or Linux + Redhat. The OpenBSD team also owns a number of other projects - everything from OpenSSH to PF, OpenBGPD, OpenNTPD, OpenSMTPD, OpenIKED, LibreSSL, pledge and unveil, their own set of perl patches, etc.
I'd say that less lines of code seems to correlate with less bugs in absolute numbers, which works out as more secure for those who don't need the extra code.
