Get the ECC RAM.

Yes, 16GB ECC is better than 32GB non-ECC for a budget file server. A file server’s job is to store and serve data reliably, and ECC RAM prevents the kind of silent data corruption that non-ECC can let through. 16GB is plenty for file serving — even with multiple users or some basic Docker containers, you won’t hit that ceiling.

The price difference between 16GB ECC and 32GB non-ECC is usually small (maybe $20-40). That’s cheap insurance against a bit flip corrupting a file or a ZFS pool. Non-ECC is fine for a gaming rig or a dev machine where losing a compile is annoying, but for data you want to keep, ECC wins.

And if you’re using ZFS (which you probably should on a file server), ECC memory is strongly recommended, though not strictly required. Don’t ruin a whole array over $30. Buy the ECC.