I've benchmarked it, and the "here's a repo, find bugs" approach finds far fewer bugs. Like, dramatically fewer. Models are good and contexts have expanded, but focus still wins with hard problems. You could probably tell the good models to make a plan to audit the repo, and it would end up making its own "loop" in the form of a checklist of files to look at over several sessions or via subagents, I assume.
Not sure if helpful but in my experience when something a bit more complex needs to be done, manually making it read the context I know the model will need for it to solve it well (like making it consume all the project docs first) helps with getting a more satisfactory result instead of only giving it the task and let it look around and consume the context it thinks it needs.
Will test your bug finding method in a current project of mine both with my "manual" context preloading and without.