This thread reminded me that the $100 RIO Technical Trout DT3F line currently on my reel, doesn't cast as well with my 7' 3wt Imperial as the $40 Mainstream Trout DT3F line I was using before my vacume cleaner got a hold of it.
I thought a better quality line would improve my casting, I was wrong. Live and learn.
Bam, I ordered the line in the link you shared. Appreciate it.
I'm not familiar with the characteristics the 7' 3wt Imperial, but the Rio Technical Trout DT3F has a long front taper, as long as 9' - 10' (DT versus WF) and it is "true-to-weight" meaning a 3 wt weighs 100 grains.
The Rio Mainstream Trout DT3F has a short front taper (the specs are not on the website but I assume that means 6' - 7') and it is slightly heavier at 114 grains. BTW - The Rio Mainstream Trout WF3F is a FULL size heavier at 120 grains.
So for reasons unrelated to price, the Rio Mainstream Trout DT3F and the Rio Technical Trout DT3F are two different performing lines. Allow me to offer a
long winded 😴 explanation why, assuming you are fishing small streams, making short casts with your 7' 3wt Imperial...
When using the slightly heavier Rio Mainstream Trout DT3F line with a seven foot leader on a cast of 20 feet, this is what is out past the tip top:
7 feet of leader
6 feet of front taper (not much weight)
7 feet of line belly BUT a slightly heavier belly so maybe 7 feet is equivalent to a 3.4 wt fly line belly.
You probably prefer the Rio Mainstream Trout because on short casts, you are getting some of the actual line weight in the belly involved out past the tip top. In addition, that line belly is slightly heavier so even though the cast is short, your rod is loading & performing to your liking.
This performance is similar to what many small stream aficionados get on short casts using a line a FULL size heavier than listed on the blank. This works similarly because the full size heavier line loads the rod with less line involved even if the rod is faster or the leader or front taper is longer.
Now revisit performance at the same casting distance (20'), with the same rod and leader length (7') but using the Rio Technical Trout DT3F line. On a cast of 20 feet, this is what is out past the tip top:
7 feet of leader
10 feet of front taper (not much weight)
3 feet of line belly BUT this time, it's a true-to-weight belly and you only have 3 feet involved so maybe the weight is equivalent to a 2.2 wt fly line belly.
You could improve the performance of the Rio Technical Trout line in this scenario by fishing a shorter leader, because every foot off your leader means another foot of line belly is involved.
Conversely. if you extend that cast another 10 - 15 feet to 35 feet and get more of the belly of the line involved, the rod will start to feel closer to the way it feels when using the Rio Mainstream Trout DT3F line on a 20 foot cast.
So IF I am right and you are fishing close on your rod, I would assume the more expensive Rio Technical Trout DT3F line sucks in close but maybe isn't so bad on longer casts.
This would also assume the Rio Mainstream Trout DT3F line is great in your normal casting distances but maybe overloads your rod a BIT on something longer. The longer cast overloading feeling would be exacerbated IF your rod is slower but if you never really cast that far with that rod or it is fast, it might not feel like the rod is overloaded.
In summary:
IF you want to make make consistent short casts, long front taper lines suck, regardless of their price. A long leader, big or heavy flies and a fast rod makes the situation even worse.
Overweight lines or over-lining will overcome some of the lack of performance in close but performance will suffer on longer casts, especially with slower rods.
This explains why I am a fan of Scientific Anglers Mastery DT lines. My trout rods are all moderate action and they love being pared with the recommended true-to weight line size written on the blank.
The Mastery Trout DT is true-to-weight with a short front taper (4.8' on a 3 wt line) so on short casts with a short leader my rods load great. My usual small stream leader is only 5' - 6' so that makes things even better. However, IF I fish this line on longer casts, the rod isn't overloaded.
As for me, I don't feel a need for BS "technical" long front taper lines ANYWHERE and I fish places like the Letort all the time. When I want delicacy, I use a longer leader and check my cast so my fly comes down softly.
YMMV - But I hope this helps to explain why line tapers and weight have more to do with performance than price.