In reply to Michael Sumner.

Without having run any benchmarks yet, I'd say RAM/memory consumption. Depending on your usage, you might see an improvement.

For example, for one of my SaaS's, I'm running arount 10 nightly CRON jobs, very memory intensive (and slow, as they use cURL). I'm fine with it because it runs at night. I know that, by using PHP 8's JIT, I would definitely see an up to 20% RAM consumption decrease, which is really good.

Coupling this with a few more updates I'm planning, such as Apache 2.4 and full HTTP/2 cURL, I expect my 10 CRON jobs to be ready in half the time (which is around 10 minutes right now).