Hey Paul
thanks for opening up a new thread on this subject...
I was asked this question when we doing our interviews for the Live DVD we did with Cara. And yes, it is a lot different and both can be fun.
In session, I am trying to provide a solid beat, nothing fancy and keep things together. This is how I always try to start. If I am playing with people I know and there are no rhythmical problems in the session it might get more fancy later on. But the goal is always a groovy session. Youtube happens to have this video of Cara
playing in a session and I am bringing this in here just to show my ideal session sound and groove. Not provided by me alone, but by the rest of the players. This came close to my ideal session speed and groove:
http://www.youtube.com/watch?v=5q2EUUwELv4
(embedding isn't allowed for this video...)
In a performance, the spontaneous character is somewhat lost, since there are arrangements and my playing differs a lot even during a performance: Playing drum kit like for some songs, playing bass type stuff for slower songs and playing trad style in some sets.
Just some random thoughts..
All the best
Rolf