It has 2 pros over MIM that i've seen.
1) You are ready to go after install. MIM is like a delish sandwich. But you are only given the bread, you have to fill it yourself.
2) Because of gay WLMs popularity lots of people use the Plus addon with pointless coloured names. In MIM you just see a code. Pidgin you don't. edit: not entirely true!
But MIM default is super light!