I agree with KCW - whether I wear tartan or plain colour kilts depends upon my mood at the time of dressing, the weather, where I am going (or what I am doing). Having said that, when I take delivery of a new kilt, I often find myself wearing it all day and even on consecutive days too - that's from someone who usually has at least one change of kilt during the day, and who normally tries not to wear the same kilt two days running.

As for feeling more at ease in one rather than the other: that does not come into my equation since I am totally at ease in any kilt I possess!