Harnesses are overrated and only peddled by an industry eager to separate you from your hard earned cash.

Only Kiddin. It is entirely personal preference. Most use waist harnesses for the reason you described. Just be aware that when you are learning and regularly have the kite at 12 o'clock, a waist harness is going to ride up a lot whereas a seat harness can not. I used a seat harness for my lesson and took home some fair old bruises on my upper legs from the buckles when pulling my knees up for board starts. They obviously aren't compatible for me but there are plenty of people out there that use them so must be some pro's.