Janus -

I like a double taper lines on my 3wts because : (1) I use 3wts on smaller water where casting distance is not a factor ( and even when I use them on bigger water most of the fish I catch are within 20-30' ); (2) For my rods, a double taper loads better in close and is easier to roll cast and mend; and (3) Since I never get the middle 20-30' of line off the reel, when one end is worn, I can just swap ends and have a fresh fly line.

But so much depends on what is the "true" line weight for any given rod, the action of the rod and the preferred casting stroke of the individual, it is best to experiment with a variety of lines, and on the water if that is possible.

Good luck.

John