Re: best aikido you have seen
IMHO, the best aikido must be felt (i.e. having personally been thrown/locked) rather than seen. By sight, a 6th kyu's aikido and a 6th dan's aikido are on opposite ends of a scale. By feel (soft, subtle and leave you wondering how you ended up airborne or on the mat), they should also be on opposite ends of a scale.
IMO, good aikido equals soft, subtle and effective - minimum effort with precise kuzushi. Power comes from the heart, regulated by the mind, absolute control over ones ego and emotion. To feel good aikido, one has to take honest ukemi - no choreographed moves and no charity fall. One just does not have the will and ability to counter - no opening to do so in the first place.
At the last 9th IAF in Tokyo, I resolved myself to take ukemi from senior shihan. At the opportunity, I would make a beeline to the shihan sitting at the edge of the mat. I was granted the opportunities to feel the "magics" of Tada, Tamura, Isoyama and Nakao shihans and had my techniques jammed by them. Those were great learning experiences, absolutely out of the scale and humbling ones too.