The zoom will be more versatile. 85mm is pretty long for a walk around lens.
That 24-70 is part of the holy trinity... with the 12-24 and 70-200vr being the other two.
The 70-200 is THE lens imho. I love this for portraits.
Here's another thought.
Get the 24-70. This will cover most of your bases for now.
Later, you are going to want a macro for tank shots, right? Get the 105vr. Awesome lens and makes a great portrait lens.
The 85 i would get only if you really really want a dedicated portrait lens. It will excel at this. I just question whether you need that right now.