I think Kururunfa is the most beautiful kata, but my best is Seisan (Naha version, not Shuri version). I practiced Shuri-te, too, and like Wansu and Kusanku-dai, though I find the Goju kata are easier on my knees.

Not sure why... it's just that Seisan always "made sense" to me, physically, and my teacher said it was my best form.