As someone else mentioned, the Z is stiffer with a faster action and the SLT is slightly slower and more sensitive. I prefer the SLT - I have one in a 6 wt. Some people say that one disadvantage to the 6 wt SLT is that you cannot throw heavy flies with it. I have found that I can easily throw big flies if I adjust my casting style, but then you have to adjust to a certain extent with any rod. Bottom line is that if you prefer fast, stiff rods, go with the Z-Axis. If you have a slightly slower casting style, go with the SLT.