I've used both. It depends on how personal your personal email is. A custom domain is only worth the expense and trouble if your email address is in any way part of your first impression.
If you are just giving this address to the services you sign up for, friends and family then GMail/Outlook's reliability actually make them preferable to setting up an email server on your domain.
Fastmail et al sell their paid service on a promise that you see no ads, and the contents of your emails will not be scanned by the same automated services that Gmail/Outlook use. This doesn't translate into better sending/receiving of email and depending on who you are, you can decide how much that extra privacy is worth in terms of dollars.
The privacy aspect isn’t a major concern to me, not because I don’t care, but certain services link into gmail better.
I also find that Google’s UX is better for me than others, and from years of using gmail I am used to the options, but was unsure if it was worth “upgrading” to a private domain.
Do remember that for "a free service" that you are not the customer, you become the product to be sold to advertisers in that situation.
You also become subject to the whims of "the free service". Should they decide to "alter the terms of the deal" you have only the options of "pray they do not alter them further" or "leave". And as to whether you can extract your data so you can "leave" intact, well, that is one of those deal terms where they set the rules, not you.
This is why I’m thinking of using my domain and aliases.
However if I use google workspace you get restrictions, however for now, these restrictions don’t apply to me as I’m mostly Apple not google, I just like the google UX.
If you are just giving this address to the services you sign up for, friends and family then GMail/Outlook's reliability actually make them preferable to setting up an email server on your domain.
Fastmail et al sell their paid service on a promise that you see no ads, and the contents of your emails will not be scanned by the same automated services that Gmail/Outlook use. This doesn't translate into better sending/receiving of email and depending on who you are, you can decide how much that extra privacy is worth in terms of dollars.