The DT line will mend better only if you're working with more line out than the length of the typical WF head. 30-35 feet.
If you're fishing a shorter distance, then the mass of either line will be about the same and there's no real advantage to the DT.
It's only with long distance mends where the DT line shines
My suggestion is trying the Cortland Trout BOSS line, it's got a really long head so from a fishing perspective is much like a DT line, but it isn't completely DT so doesn't take up so much space on the reel. Not to mention it's taper is extremely well designed, basically the best of both Worlds when you consider the benefits of both WF and DT lines.
Been fishing it on my 5 wt a lot past few weeks with an indy/nymph rig and am really impressed, just got one for my 4 wt as well, but have yet to fish that one.
Edit: I like that line! 100' with a 65' head, etc. Need a new 7wt line for my Sage XP. Think I've found 'My Boy.'
I think this line would excel for dry line steelhead fishing, I plan to try one this Summer on my seven...
Just for the heck of it I messed around with a long lead and soft hackles on my five, it was nice, very nice...
One thing you may think about, if you plan on carrying a lot of line outside the tip, under-lining the rod...
The BOSS Taper follows AFFTA standards regarding the first 30', but obviously with such a long head if you start talking 50'+ outside the rod tip and you are fishing a 5 wt BOSS on a 5wt rod, the line becomes more like a 6 wt or 7 wt line as an example.
5wt BOSS at 30' is 140 grains
6wt BOSS at 30' is 160 grains
Under normal fishing circumstances I would never really see under-lining being necessary, unless you were doing something which long casts were the norm like swinging flies on a dry line for steelhead can require, then I would likely under-line by one weight with this line. Maybe some long distance dead drifting of dries under-lining would be nice as well. Have yet to run into any circumstances that would fit that bill, not doing much dead drifting of dries in the Winter
Location: White City (tad north of Medford) Oar-E-Gone
Re: DT or WF lines?
Good call there, good call. Even with a single hander 95% my 'casts' are done 'spey style.' Tight quarters behind and rod doesn't know, or at least a Sage XP doesn't know/care.
Need to think that through and/or call Cortland later this AM and get their 'take.'
Edit a bit to elicit further comment.
Vast majority of my fishing is with 2handers, but there are places on the upper Rogue where even a 'switch rod' at 11' is 'over kill. Holding water is beach out to maybe 40 feet. Beyond that and the water is really chugging along. One of those is the center part of 'Denmon.' Another is the 'Hatchery Hole' (aka Zoo Hole, and you can guess why) down to Casey. As all that water is pretty much dam out flow the 'slots' where the fish will run are well defined and little changed in the 15+ years I've fished same. A 30' cast can be over kill, or to put that another way, you've cast right over any moving fish and you loose/pizz away 1/3 of your drift. High stick nymphing at its best?