It really depends on the size I believe, the big bang effect is that if you had the initial rewrite, it's going to be very fast and fairly reliable. But past a certain size and complexity the architectural decision it makes on portion of the project then trends to become negative holistically.
The vibe coded software I've written has a very steep dropoff rate for bugs. There are a few at the start, you get Claude to fix them... then occasional bugs for like a week, and I haven't had to touch the code since.