Was a big fan of Pradco Excalibur and Super Silver Thread, but they apparently went out of the line business. Both were rather large and perhaps stretchier than others, but I liked them. McCoy's is good stuff, and relatively easy to get. On recommendation of some BBC regulars, I've tried P-Line CXX and found it to be tough but somewhat curly. Lately, I've been trying out Sunline Super Natural and should measure it, but haven't yet. It seems quite small for the 12 lb test I've been using on Shakyheads and "Bubba Drop Shotting" (baitcasters for both). I'm not entirely sure about the durability side of it, but it is nice to use and worth a try. I tried 10 lb Izorline of some type on a spinning reel and found it to be absolutely horrible from a memory pov. I stripped it all off in the boat and reloaded with McCoy's, and that's the only time I've ever gotten that PO'd at any line.
I would like to add that our club had the original owner of McCoy's come and talk as our entertainment one month. He said that Monofiliment is made from one type of nylon, while CoPolymer was made from more than one type of Nylon. He said there were many types of nylon, and I think the number was around 56. The combinations give various traits that are sought out, such as pliability, stretch, strength, etc. Sadly, the terms "mono" and "copoly" are commonly mixed and I'm not sure even the line manufacturers label is trustworthy on this. Does it matter? I kinda like to know what my line is made from, and oh, yeah, I've tried several Fluorocarbons and think it's mostly hype and $$$.