And while more drives means more failure opportunity, it also means when a failed drive is replaced, it’s likely of a different manufacture period.
I have a 5-drive NAS that I’ve been upgrading single drives every 6 months. This has the benefit of slowly increasing capacity while also ensuring drives are of different ages so less likely to fail simultaneously. (Now I’m waiting for prices to come back down, dammit).



Others have mentioned power - you may want to do some math on drive cost vs power consumption. There’ll be a drive size point that is worth the cost because you’ll use fewer drives which consume less power than more drives.
Having built a number of systems, I’m a LOT more conscious of power draw today for things that will run 24/7. Like my ancient NAS draws about 15 watts at idle with 5 drives (It will spin down drives).
More drives will always mean more power, so maybe fewer but larger drives makes sense. You may pay more up front, but monthly power costs never go away.
Also, I’ve built a 10 drive n NAS like this (because I had the drives and the case, mono and ram). It can produce a lot if heat while doing anything, and it was a significant power hog - like 200w when running. And it really didn’t idle very well (I’ve run it with UnRaid, TruNAS and Proxmox).