I don’t like how gmail shows ads even if you subscribe to Google One (I suppose this isn’t a problem on workspace accounts). I do like it’s rules to auto tag emails and the ability to set your own tags and rules.
Outlook app is a little bloated but it’s more functional than the native iOS mail.
Gmail is probably my favorite but since I transferred my domain to cloudflare after Google domains sold to square space, I’ve decided to use iOS mail again with my custom domain