I always tie an Improved Clinch knot to the jig (or a regular hook) ... but I do use loop knots on my leaders where they connect to the main line (but that's simply for convenience).

Loop knots are being used to allow the jig to hang "naturally" (horizontally) when being retrieved or when a vertical presentation is used ... with the idea that a tight knot on the jig eye would not "slip" as the jig changes direction (when casting) or would be "off center" when fished vertically, causing the jig to be at an angle (or in an un-natural position). All of that is based on the assumption that a jig will hang horizontally ... balanced, if you will, by the weight of the jig against the line connection to the top center of the jig eye. That isn't "always" the case IMHO .... but it is sound reasoning, most of the time. The size of the hook, density and/or length of the plastics attached, or even the style of the jig vs the weight of the lead head of the jig can alter that balance.

I, personally, just have more faith in the Improved Clinch than I do in a Loop Knot, as far as the breaking point @ the knot. I've had too many instances where when Pushing jigs & getting hung, I've had the leader break at the knot & I retrieve nothing but the "loop" still attached to the duo lock clip. Rarely have I broken off a jig tied with the Improved Clinch, where I came back with any portion of the knot or an indication of the knot on the empty tag end. I've also noted how the jig swims thru the water, when tied with the Improved Clinch knot ... in the conditions of very clear water (>3ft visibility). The line is generally in an elongated reverse ~ shape .... coming down from the rod tip, then leveling off about midways, then dropping towards the jig (due to the weight of the jig vs the resistance of the line against the water). This basically puts the jig in a slightly head forward diving position or a near level horizontal position ... depending on the speed of the retrieve ... both of which are "natural" positions of a fleeing prey species.

That being said ... like so many other things/factors in the world of Crappie fishing ... a lot of the time it boils down to personal preference and/or confidence, since the results are usually nearly equal in the outcome : ie - the fish bites the lure.

It's a lot like the difference in how I tie my jig on & how one of my fishing partners ties his on : I cut the tag down close to the knot, my partner does not & may have as much as a 3" tag sticking out. We're both using the same hi-vis line & the same knot. He often gets just as many hits, or catches just as many fish (or more). IMHO ... if the hi-vis line was a deterrent to a fish biting our lures, or the presence of that extra piece of line (representing a loop knot, sort of) was a factor in him not getting hits, or the position of our jigs wasn't "natural" due to being tied on with a Improved Clinch knot ... then we wouldn't be catching many fish. We have, we do, and we will continue to do so.