Oh I totally agree! I was shocked they would argue about efficiency without first benchmarking the whole program and identifying that code as a chronic bottleneck! (I only did the benchmark because I was bored and curious on a slow Christmas/New Year holiday).

On Coding Standards and Code Reviews summarises my opinion:

• Correctness, simplicity and clarity come first. Avoid unnecessary cleverness. If you must rely on cleverness, encapsulate and comment it.
• Don't optimize prematurely. Benchmark before you optimize. Comment why you are optimizing.

For much more detail on this topic see:

• on Code Optimization and Performance References