I'm kinda biased, but i think irose is the most fun, just beacuase all the clients are kinda old so you dont have to hunt around for the client that will work with osrose.
So i would pick osprose or osirose.
Here is a guide for osprose: viewtopic.php?f=39&t=1715
Here is a guide for osirose: viewtopic.php?f=27&t=4242
and if i can't convince you, here's a guide for osrose: viewtopic.php?f=27&t=33
Heres a bunch of clients: viewtopic.php?f=27&t=1510&hilit=client+download
You dont need the [URL] ~ Sethanye