Quite an interesting cross section of opinions.
A few observations.
Many of the copolymer tippet materials are of a narrower diameter than the equivalant breaking strain of Florocarbon, in fact only a couple of specific brands of Fluoro are thin, most get by on being clear and the theory about light refraction.
Something else to consider is many of the "Fluorocarbon' lines are nylon coated with fluorocarbon, not a pure material, these lines tend to be cheaper and thicker than good co-poly.
Personally i like fluorocarbon as a tippet (particularly Grand Max) but i don't like the fact that it doesn't degrade in sunlight, which is why i don't use it. So i tend towards clear Co-poly as it does a similar job, but has better knot strength (although both materials require wetting prior to tightening) and is a bit more environmentally friendly.
Stiffness is another issue, i would imagine that making a leader material stiffer would increase its potential for memory, however if you rub it with your fingers to get it warm while stretching it then most tippet straighten out with no real problems (i've done this with 60lb saltwater tippets
). I use Frog hair a lot and find it has a nice balance of stiffness and diameter. How you would quantify this i'm not quite sure
.
If a leader is too limp then it will not turnover, if it is too stiff then you lose the subtle presentation that your fly line is giving you with its tapered profile.
Obviously the length of the leader also has a bearing on how stiff or limp it is, i suppose this is why i tend to use a 7-9ft tapered leader with a fairly stiff tippet. it gives me the continuation of the taper to get the presentation but also the stiffer tippet to turnover the fly. my tippets are rarely longer than 6 ft (usually 3ft of level diameter, with another 3ft stepped down for droppers), with most leaders, i'd be looking at 10-12ft single fly and 12-15ft for 2 flies
Fly size and style will have a bearing on this as will the profile of the fly line.
Lots of variables with no correct answer.
However if the question is colour or diameter, i'd always go for clear, preferably matt and use whatever diameter suits the fly i'm fishing.
So i'd like a narrow, fairly stiff, matt clear, co-poly, with good knot strength, little memory and the ability to cut through the surface film and sink very slowly
Sandy
Not much to ask for