Do I understand this correctly:
Ueshiba, very soft training methods, hara dominant, pretty circular
Tohei, still pretty soft, more linear
Shioda, seems to be much harder, much more explosive, and sometimes extremely linear.
With a couple of minor caveats, I'd say yes, there are differences along those lines, Ron. But someone who has only learned one approach is not going to fully understand all the ramifications... and worst of all, it can lead to someone teaching/leading people down a hard-to-change path (the why is pretty easy to show).
Just to complicate matters, though, divergences can and do start anywhere. Generally, though, you can see that different approaches by Ueshiba, by Tohei, and by Shioda led to (some of the better) students of each having a noticeably different flavor to their Aikido. It's a good topic and will merit more discussion in the future times.
It would seem to me stressing either Ueshiba's methods or Tohei's methods could still lend a great deal of progress in moving in Shioda's way...but perhaps not so much in the other direction?
Oh, I agree. Everyone needs a foot-in-the-door to the basic skills, but the divergences will start at that time of foot-in-the-door, too. So it's worth thinking about. I realize that not everyone will see the problem, but it's just one more of the many "I.Q. tests" that are part of learning these skills.