I get the thought, but your phone can also have a security breach at any moment, ESPECIALLY because normal user error is by far the weakest and most often exploited attack vector.

Bitwarden's vaults are also encrypted with the option for even stronger argon2id encryption. Bitwarden themselves can't access them or reset them. It is open source and most importantly, audited. KeypassXC has only had one audit ever. (Though that passed and I would also definitely recommend keypassXC, it is great software security-wise)

The database is stored, encrypted, once on their server and once to each device you sync to, so it is available locally.

Even if they had a security breach, by design the assailant couldn't access your database any more than they could access your keypass database.

You can also self-host it which would bring it exactly to the level of keypassX variants as far as attack surface.

Not to mention with bitwarden, you will also only need one key. That is the whole point of a password manager.

"It is available locally and a lot better..." is simply untrue. They are both great options. Just whatever works best for the person. Bitwarden has a ton more QoL options and enterprise options, plus separate, shared password databases and such for families and companies. Again, just as secure.

I have a lot of experience with both. As a tech savvy user, I slightly prefer KeePass. Syncing between devices is slightly more painful, but I find it to be more reliable, and it doesn't have the attack surface that Bitwarden does. (While encrypted, Bitwarden still really wants a web server and a local database connection.)

VaultWarden is probably better for those who can't be bothered to move a file around and want direct browser integration. With KeePass when you need a password, you'll make sure the username has focus and then alt+tab to KeePass and hit "autofill". Some sites won't take "username{tab}password{enter}" and you'll have to customize the configuration.

VaultWarden is better at prompting you to add new passwords. I prefer the workflow that's encouraged by KeePass, where you open the app first and use the app to open the URL. (You can do this in VaultWarden too, but it's less obvious.)

While I personally use KeepassXC and Keepass2Android on mobile devices (as with KeepassDX there is no reliable way of syncing the database that I know of) to other less tech-inclined people I'd always recommend Bitwarden as it is much more suitable to most people's usecases.