Although I trained at Hombi dojo in Tokyo during a brief visit, I based my no vote on that plus my experience with Aikido people who had trained for extensive periods.
I would say that there was a time, a sort of Golden Age of Aikido training in Japan during which the training was really cooking. But if you look at it now, although there are still wonderful teachers most of the old legendary teachers are passing away. Some of the most dynamic and talented teachers have moved overseas.
When I look at the training I recieved from Saotome Sensei or at the quality of students being turned out by Chiba Sensei and Imaizumi I know that it would be difficult if not impossible to duplicate that in Japan.
And then that first generation of American teacher is now here and they are some of the most talented and creative teachers of Aikido you could find. Mary Heiny , Tom Read ,Clint George , Linda Holiday, and Jack Wada Senseis are all products of Shingu having trained under Hikitsuchi Sensei and his deshi. You couldn't find a better experience in Japan than training under teachers here of that calibre. Other teachers who come immediately to mind are Bruce Bookman Sensei and Wiliam Gleason Sensei. You don't need to go to Japan to have training of the highest quality and it you would have to look around to duplicate the kind of training you could get from teachers like these. I am sure that there are more teachers I could mention but these are all folks with whom I have personal experience.
Aside from the cultural experience and the possibility of doing other training that would be difficult to find in the US, Japan has nothing on us.