Bruce Richards, who knows a bit about fly lines, wrote the following two articles:

www.flyanglersonline.com/begin/101/dtvswf.php

www.danblanton.com/WFvsDT.html


Most of the line Manufactures publish the technical details and measurements of their line tapers on their websites and/or print catalogs. If you look up this material you will find that the front 30 to 40 of basic WF and DT lines are often the same, in which cases there is no difference in performance until you get into the back taper of the WF line.

Now there are many specialty tapers available that it is difficult to make a blanket statement that a WF or DT is better for presentation. For instance some DT lines have a longer front taper for more delicate presentations. But some WF lines do too. In my fishing I really haven't found there to be a significant difference, the ability to make a good cast having a greater impact on presentation.