My first password manager was 1Password. Starting to use it a year or two after the release. Used it a few years, moved to Apple Keychain, a couple of years later back to 1Password, then back to Keychain. Been using Keychain since.
When 1Password 8 was released I went back to 1Password. It looked great, but as you put it, it was more clunky to use. You have to download the app and the browser extension. It require more steps to use, and had some errors. Keychain is more fluid and better integrated. A few days later I was back to Keychain, and been there since.
What I liked about 1Password is the way it look, and I could store my passwords, credit cards, important documents and notes, driver's license, software licenses and more in one place. With just one password to remember.
Also liked it was an app, unlike Keychain.
I ended up with a shortcut on my Mac, iPhone and iPad, so now Keychain function as an app. (almost).
For documents, notes etc, I use locked Apple Notes. Unfortunately you can not lock Notes with files, hopefully Apple will add the function soon.
Keychain looks bad compared to 1Password, in 1Password, if some site icons was missing, I made my own. (Hated to see a missing icon). Keychain looks messy, but is made to be in the background. No need to open Keychain and check your passwords, they're always there in the background. It just works.
1Password is probably a bit more robust and safer, thanks to the secret key, but Keychain is safe enough for me.
Someone need to physically have both your device and biometrics to get in. And since most people use biometrics, on 1Password, it's the same there.
To my knowledge 1Password and Keychain is pretty similar. Both have the same level of encryption.
It's easy to import your logins from 1Password to Keychain.
English is not my first language, but I hope my experience could be of some help.
Recommended reading: https://medium.com/macoclock/i-switched-from-1password-to-keychain-heres-why-328806e9141
