The thing people tend to gloss over is how CoW shines until you need to update the base image, then you start playing whack-a-mole with stale memory and hotpatching. Snapshots give you a magic boot, but god help you when you need to roll out a security fix to hundreds of forks with divergent state.

Fast startup is nice. If the workload is "run plain Python on a trusted codebase" you win, but once it gets hairier the maintenance overhead sends you straight back to yak shaving.