I havent cast the Orvis, but I've played around with most of the rods in the Z-Axis and the BIIx line. I really like the BIIx 4,5,& 6wts, there really smooth, really light, and they have a soft tips. The Z-Axis is a little faster, and lighter than the old XP models, faster than the BIIx, but not as fast as the old XP's. Frankly, I like the Sage SLT and better than the Z-Axis.
The SLT 590-4pc is a real honey, wish I could fish mine more often, but its my wife's favorite fly rod. The 8.5' 5wt BIIx is a great rod too. Cast them and see what you like best. Cheers.