- from what I see owncloud is now written in go whereas nextcloud is still PHP. That might give it a performance boost on a raspberry pi (it basically avoids all the overhead from reading and byte-compiling all the PHP files on every request)

There are things that you can do to speed up nextcloud though:

- look into php byte-code caching (opcache and stuff like that)

- make sure your database indexes are set up correctly: I can't remember where in the admin ui (I'm on the phone rn) but there's some sort of self-test/diagnostics page that will tell you about database indexes to create (and the SQL commands to run too, iirc)

- you can tell nextcloud to use a redis for caching too, that could give an additional performance boost

But yeah, again, the raspberry pi isn't really that good for this kind of things. For pretty much the same (total!) Price of a RPI and related accessories I'd get something like a Lenovo m93p tiny off eBay and slap an SSD into that. You'd get proper performance albeit with a higher tdp.

I hope this helps :)