I just switched from iOS to deGoogled Android (e/OS setup by Murena) and as discussing with a friend yesterday, the biggest trade off is arguably security, namely than iOS and AOSP are relatively secure (even though far form perfect) and applications have both permissions to explicitly request and also containerized (e.g. limited file system access) ... yet you do not need a security flaw to exist if your data are being exfiltrated periodically by the OS or apps. So arguably depending on your thread model (e.g. voluntarily offering your data vs spam/scam vs private malicious actors like NSO vs state level espionage) and your needs (banking apps vs Web equivalent) then one can be more appropriate than the other.

1. A password managed is basically like a physical vault. If someone gets into a physical vault, they've gained access to all your valuable items, but the vault is extremely difficult to get into.
2. Random websites do not prioritize security like they should. So when there is inevitably a breach in one of those 50 sites and you end up on haveibeenpwned.com, that does not allow them access to the other 49 sites. Often when logins are breached, the people getting that information do not care about the actual site that was breached. Rather, they know a password you use and your email, and can now try to login to actually useful sites where people often use the same login.
3. There should be multiple layers of security to your password manager. Password and Authenticator app should be basic (No SMS or Email 2FA, not secure enough). Ideally, we move towards passwordless logins altogether so there is no secret that can be compromised on the server side.

If you use an easy password for your password manager, it's trivial to crack with a few word lists and hashcat, just as any other account.

Websites get hacked all the time, and your login details (and PII) ARE available for sale from shady people right now. It's important that, the next time one of the sites you use gets hacked, you don't have to scramble to update all your other logins.