This is not as obvious as many naively believe.

It depends on how hard to maintain the code added is, how likely it needs to change in the future, and most importantly on the cost.

If reviewing and manually improving the code takes hours, the cost may already be in the thousands.

That buys you a lot of AI usage, roughly a few months of continuous work.

You have to balance this with the chance that the suboptimal code the AI generated is actually fine and maintainable enough, and also the chance that during further work on that code a model might implement the same optimization on its own.