In this exact scenario, who is better equipped and motivated to do a good job?

1. Pilot at the end of their duty day, running around in the rain, who's only direction is to look for basic discrepancies?

or

2. Trained mechanic, dressed for the elements, with tools and training to do a much more thorough inspection?

And for bonus points, which one wins for safety?

Neither are un-safe, but one sure increases the margins of safety.