I've always found Gmail to be superior to any of the free email clients out there. Whether it be Yahoo, Hotmail, AIM, or anything else. I even prefer to use Gmail over my own personal Comcast email. Unfortunately, I don't really use my Gmail account for anything other than account related details. For instance, when I make an account somewhere. But... I change my email address like I change my underwear. Seriously. :|
The only ones I've actually used over a long period of time were two @msn.com email addresses, and maybe one @gmail.com address. But when I need to give someone like a teacher or potential employer, usually I give them either my Gmail address or my Comcast one. Which ever one comes to mind first...
But in my opinion, I've found:
Gmail > Yahoo > Hotmail
Unlike others, my Hotmail inboxes were always flooded with spam messages to the point where I grew too frustrated to use that account anymore.