Thanks guys. So I see it is not a straightforward decision. I think when I say portrait I have to clarify that I mean portraits of my-always-jumping-son and not a subject like Colin's daughter. I have to wait a few more years for that kind of model I guess, so the shallow depth of field should be a big problem for me right now.
I actually did not think of it as a big problem before, what made me think about the 85mm was these pictures from Ken Rockwell:
http://www.kenrockwell.com/ryan/2008/2008-04.htm
Most of them are so sharp and bright, makes me drool