Yahoo Messenger or MSN

I use yahoo messenger since all my contacts use it. I use YM to chat with my girlfriend abroad and sometimes talk to my school mates about projects and other works to be finished. There are also times that my professors use YM to help their students with problems and inform them of something important.

I only use msn, don't bother with yahoo. msn is just so easy to use and to be honest not a huge fan of yahoo no particular reason other than most of my english and american friends don't seem to have yahoo anyhow.