Kestrel, I've had exactly the same problem with Krystonite that you've had with X-line. Mind you, that's not surprising as I believe I'm right in saying that they're the same line!
In fact, many lines are identical as Jim Gibbinson pointed out in his excellent article "Mono Facts" here on Angler's Net. See http://www.anglersne...mono_facts.html
I also agree with Jim that there's no one best line - it all depends on the circumstances. This is because there are lots of factors involved, and if you improve one you'll probably do the opposite with another.
All you can do is to make a short list of lines that are suitable for the type of fishing you do and the waters you fish. This is what you'll find in Jim's "Mono Facts" article.
It's based on a huge number of bench tests that he did on a large variety of different lines. The full details were published in the January, February and March 1998 issues of Carpworld and don't therefore include some of the latest lines on the market.
Since then Jim has done a few more tests but not published them. However on the basis of these Jim's recently recommended that I try Shimano Catana. This is identical to Shimano Exage except that it's available in higher breaking strains and in bulk spools. Jim uses Exage in 5lb breaking strain for mullet and is very pleased with it.
At present I'm using Gold Label's Pro Gold and Pro Clear. The former came out well in Jim's 1998 tests, whilst the latter hadn't arrived on the market by then. However it did do well in Jim's later tests, as it did in the more limited tests that Lee Jackson did on dry lines for the Tackle Box.
BTW, Pro Gold and Pro Clear are different lines and rated differently. Pro Gold is rated according to its wet, knotted breaking strain and 12lb Pro Gold has roughly the same strength as 16lb Pro Clear.
The bench tests are of course only a starting point. You then have to field test the lines you've shortlisted as some in practice may have disadvantages in certain circumstances - such as Krystonite and X-line.
For my field test of Pro Gold go to http://www.anglersne...s/progold01.htm