I don't really have a preferred, more like ones I'm used to. I have Hotmail, AOL, & ProtonMail. I would say though that I prefer ProtonMail as they are more secure.
I always used outlook/Hotmail as my own personal email. But no preferred email provider. End of the day each email provider has its reasons why I use them. Like, Gmail is easy to use regards ending and forwarding custom email address.
Gmail definitely has its conveniences. For example, I like how some website and cloud services offer the option to log in using your gmail access. However, I don't use Gmail exclusively. I also have email accounts with Outlook, Yahoo!, and Apple.
Yahoo was my primary email for a very long time, but I’ve been using Gmail more lately. Yahoo has gotten ridiculous trying to force me to sign up for their premium email subscription. 😛