A while back Hillel Wayne did a talk (whose name I forget) on what empirical evidence on software quality actually says.

As I recall, he concluded that there’s really no support for then-popular ideas like short functions, reducing cyclomatic complexity, avoiding explicit branch statements and loops, or TDD. (Tests yes, just not TDD.)

He made a pretty strong case that only two principles are particularly robust. One was that limiting code volume is good. The other is that working people too hard is bad.