I keep my lines even. Easier to keep up with that way. If you want to trim one way or the other you can do that at the kite via the pig-tails. Or in some cases at the bar on the leader lines. I am a little anal about my lines being even though. If I feel the kite pulling to one side I tune my bar. I all so jump and loop in both directions to keep from stretching one side over the other.
I do agree people do not know how to trim a kite but everyone wants to call it depower instead of trim. Hard to teach people what trim is when even the kite companies and instructors call it depower.