Reclining will be more comfortable unless you just like sitting with your back almost vertical. I use the fixed back on track because the position is great for open track however the 100 mile drive to and from wasn't the greatest. Also the reclining race seats have a LITTLE more padding as opposed to the fixed back.
The fixed back I was in was the Corbeau Forza.
My 69 will be getting a reclining set of "race" seats since I plan to drive it more on the street than the track. Worst case I'll just swap in the fixed back for track events since they will likely use the same seat rail.