Noticed my better line has detereorated in SNR a little lately while my second line had improved, so out of curiosity I forced a resync on Line 2.
Here are the results of both lines before and after I rebooted the second line.
Notice how the errors have shot up as clearly they are now causing crosstalk with each other. My real-world speed has actually reduced.
(you might have to right click, view image before it will load as the forum image proxy seems buggy, you can then press back on the browser to see it in the page properly)
Also Line 2 had an insanely optimistic handback threshold when it first connected (I synced well below it but was fine with that as I knew from Line 1 it was unrealistic), as you can see this is now much more realistic.
I guess this is a good example of how theoretical stats is meaningless, at least without vectoring to offset the crosstalk.