IF you tend to ONLY throw large flies in the wind on Thursdays.... I'm sure you will find a line specific to that need.
However, I think you'll find that most fly fisherpeople will attach them selves to a brand/model or price of fly line.
I prefer DT on all lines 4 weight or less. I prefer the Rio Selective Trout. I prefer the duller colors. That doesn't mean I don't use other lines. That doesn't mean that while I like to fish smaller dry flies, sometimes I find the need to throw a heavier fly... I don't really want to switch lines, I just want to tie on a different fly...
I comes to personal likes (of dislikes... I'll never use another Airflo) or what line is most compatible with the rod of choice.
That all being said... marketing ploys abound!
Later,
Peter