HGST personally, because my failure count over time for those drives has been in the single digits through ~60 drives in around 15 years, though every manufacturer is going to have missteps or failures. I can say I’ve had bad experiences with Toshiba, but I’m sure you can find someone who swears by them also. Ultimately my anecdotal evidence in either direction is an unreliable crystal ball you should take with a grain of salt.
The suggestion to check Backblaze reports is great, but I’d also recommend to vary your manufacturers if you’re able and instead build your storage solution with the assumption that drives are “wear units” and will fail. If you have some redundancy built in where you’re able to tolerate the failure of one (or ideally multiple) drive failures without losing data, then even though the question still matters, it matters a bit less.
So—I will preface this by saying I’d also love for an alternative to Nextcloud that’s faster and more reliable.
For the combo of FileBrowser and Joplin—I used Joplin a bunch in the past so I’m relatively familiar with it, but it’s also been a while and things may have changed—how is it syncing? I seem to remember hooking it up through WebDAV to sync—is that (still?) the case? If so, does that mean that FileBrowser is also exposing a WebDAV server in addition to the HTTP server? Is FileBrowser doing any cross-device syncing at all, or is it as it appears on the surface—just exposing a folder via a URL that you can send/retrieve files from?
The one thing I’d caution with Joplin, and what ultimately pushed me away from it was the portability of the data within it—I didn’t love that I wasn’t ultimately just working with a folder of Markdown, which led me to Obsidian—but don’t let my preferences dissuade you—the best system is the one that works for you—just more of a heads up since at least a few years back the export process was a bit of a pain to get things in a “vanilla” state.