It's been years since I've used a loop knot with crappie jigs, single or double jig rigs. My thought is that the eye of the jig rubbing freely inside the loop of the line has got to create a much greater degree of wear than direct tying. But that's just the way my mind works.
I know jigs swim more freely with a loop or non-direct tie, so for many years now, I've been using "snap hooks" (jannsnetcraft.com). Although these extremely light weight metal hooks were intended for fly fishermen, I find the medium size #2's to work extremely well with 1/16 & 1/32 oz. crappie jigs. And as an added bonus, it facilitates quick jig changing (however, you do have to grip the snap hook with a pair of needle nose pliers to get the jig off and back on again). This device reduces line wear & tear quite a bit, in my experience. I use Trilene knot (with all my direct ties) to tie to these snap hooks - single or double rigs. Has worked very well for me for many years now.
"A voyage in search of knowledge need never abandon the spirit of adventure."