> Based on what metrics? Someone skilled in Assembly can and has found many vulnerabilities in closed source software. The chance of you as an individual being able to audit the entire Linux codebase and finding a new vulnerability are nil unless you have some special skills that you haven't mentioned that make you better than some of the top hackers and researchers.

Auditing C source code is orders of magnitude simpler, than auditing binary. With the same resources, you can have much more done in the former case than in the latter.