Well, I was using hotmail before outlook, but I really didn't use my hotmail for anything outstanding other than sending mails. And that's the same thing, I've been using outlook for. So, I can't really state differences in terms of features.
However, I've always loved my hotmail for it's simplicity which outlook has made even better with it's very simple and neat outlook. Truth, is no one needs all the fabulousity synonymous to most other public email services.
IMHO, outlook is more easier to use, and faster.