My 8’6″ 4wt Z-Axis is my go-to rod for dry fly fishing. It is an absolute beauty of a rod. I use it on the North Carolina small streams with heavy canopy cover and it roll casts great. My casting style is well suited for the Zed but I also hear that the ZXL is a good rod as well (I have no experience with that line). I use an orvis battenkill reel and rio grande WF fly line for a complete setup. I find that the 8’6″ length is better for dry fly fishing and smaller streams compared to the 9′ length in the 4wt rod. The rod has a good responsive feel and the flex has never been a problem for my style. I can recommend my setup without reservations.
Sage ZXL hands down. I have been messing around with some demos I got from the Sage rep in my area and the ZXL would be the best suited for a dry fly rod. The other demo I have is the Z-axis. With the Z-axis you will have a more well rounded rod for various applications, but if you want a true trout rod for dries go with the ZXL. I’m actually going to add one to my arsenal in the near future.