I respectfully disagree. I've been studying bagua (a Chinese internal martial art). It is all about turning and circles, both external and internal. I think Aikido could incorporate a few turning tricks that works better and saves our knees from potential damage. I don't think Aikido contains physical principles not present in other martial arts. Nor does it lack anything present in other martial arts (at least the arts I've been exposed to). But since the question said "budo" are we limiting the comparison to just a few Japanese styles?