Upgrading an M4 Pro Mac mini's storage for half the price

Honestly the external option seems a lot better value for the money for almost all use cases. Something like half the cost. No tinkering with the internals of the very expensive thing. You can move it between computers, upgrade the stick in it, etc.

I'm sure there are cases where you really do care about speeds >3GB/s (and USB-4, the port on the mac, should max out at ~5 which is still marginally lower than the internal one). But I doubt they are common. It's hard to process most data in a meaningful way that fast.

My only nit with that is that with external storage there’s definitely a race when it comes to mounting.

More than once I’ve had, say, Photos complain that it couldn’t find its library because I have apps relaunch on startup, my library has been moved to external storage, and the drive was not ready yet.

Also there’s no guarantee, at least naively, that what was /dev/disk4 on the last boot will be /dev/disk4 on this boot. Normally not necessarily an issue, but if you care about actual drive devices vs volume names, it can be an issue. (And there well be some low level config file wizardry to fix that issue, I just haven’t bothered to research it.)