JM, the reason for recommending a seat harness is that you will find when you are learning you fly the kite overhead a lot of the time: bodydragging, walking back up the beach, water starting (& stacking - fun

). This will continually cause the harness to ride up into your ribs, making it uncomfortable.
I have just changed from seat to waist harness and love the waist, but am glad I started out with seat. You may prefer a waist from the start, but it pays to be educated in why ppl choose different styles. Also if you have back problems, most ppl find a seat harness is better in preventing back-related issues.