Shortrod,
That's a great link you posted with info about WF vs. DT lines. What is written there that you disagree with and call "propaganda?"
Lines
Every few years, there seems to be a debate on WF lines vs DT lines. This age old debate is more fueled by false assumptions than true facts. Of course, if you like DT lines, continue to buy DT lines. If you like WF lines, continue to buy WF lines. Stick with what works! Which is better really depends on the specific line and the specific application.
First, yes, it is true that a DT line can be used twice if you're willing to turn it around and reuse the other side. No, this is obviously not an option on a WF line. So for the budget minded angler, a DT has some appeal.
It gets a bit more complicated when people claim that a DT can pick up easier, can carry more line, can mend better, and the favorite, can roll cast better than a WF line. All of these claims assume that you are fishing distances beyond the rear taper of the WF line. If you are fishing distances less than the length of the Front Taper+Belly of the line, you are virtually fishing the exact same line.
DT:
Until you reach the rear taper of the WF line, these two lines are identical. For this specific line, the Front Taper and the Belly add up to 28 feet (for the WF-5). Add a 9 foot leader to it an you're now at 37'. So if you have out 37 feet of line out or less (assuming a 9 foot leader), you are fishing the same line. It'll pick up the same, carry the same, mend the same, and yes, roll cast the same.
Once you go past that 37' foot mark, things change.
The WF line will allow you to shoot the line since a thin running line goes through the guides much better than the thick belly of the DT. On the flip side, the DT can allow you to carry more line since a longer head usually always translates to more line control at distances. However, there is a point that it becomes difficult to carry a significant amount of line due to the amount of weight beyond the rod tip and at this point, a DT become more cumbersome than a WF line. You may find that by shooting a WF line you can achieve greater distances more efficiently than a DT line.
This same principle applies to picking up line. Picking up more than 37' of line off the water and generating enough energy to cast can be difficult, no matter your casting ability. It's simple physics - you cannot generate enough speed with the rod to move that much weight of the line. This isnt to say it cannot be done, longer rods can help with this, but it is difficult, especially with lighter line weights.
The 'DT lines mend better' argument is probably the most sound of them all. More thick line in the rod tip, the more control you have on the water. However, unless you're stack mending down stream, nymphing presentations beyond 37' are pretty ineffective and pretty susceptible to drag. Not only that, again, it's pretty difficult to pick up more than 37' of line (see above argument).
And then there's the favorite, 'DT lines roll cast better.' Roll casting more than 37' with a 6 weight or less is pretty difficult. Unless you are a skilled single hand spey caster, you're not likely to roll cast beyond 37'. Again, it can be done and longer rods help, but it's difficult. Furthermore, if you are roll casting beyond 37', a WF line will give you even more of an advantage since the transition to a thin running line will buy you even more distance! Take a look at a skagit line's taper and you'll understand. There's a reason all spey lines are WF.
Remember, all this hinges on whether or not you are fishing beyond the length of the front taper+belly (and dont forget the leader length). Those that fish small streams or pocket water will rarely cast beyond our example of 37' and most lines on the market happen to have a front taper + belly that's 37' or beyond. So aside from the fact that you can flip a DT line around, there are virtually no differences between the two lines until you get beyond that 37' mark.
Again, get what works for you! If it isn't broke, don't fix it, right? But next time you're chosing a line and someone claims DT or WF is best, understand why.
Link to source: http://www.scientificanglers.com/insider/2012/04/wf-vs-dt-debate