Also, with your own domain, you can start on a hosting platform (we're on Fastmail for our business domain, because one selfhosted email server is quite enough thankyou) and later move to selfhosted, OR vice versa if selfhosted gets to be too much. You might have to move your email history around, but people sending email to you don't have to know or care, you've still got the same address.
And if one email provider screws you over, you can just MOVE, and keep your address!