Could you then explain (or point to me a post, website, whatever) what the very nature is of Daito ryu and of aikido and how these natures are polar opposites? Because I can't see how two arts can share so many techniques, but use these to achieve totally opposite goals.
I hope that you don't mind if I chime in here? I don't want to usurp Shaun Raven's reply, should he choose to do so, but I'd like to make a distinction here about my views of DR and Aikido.
Pre-war, Ueshiba taught DR. Little, if anything, was different. So, I won't focus on that part of Ueshiba's life at all. It's same-same as far as I'm concerned.
It's after he broke from DR that becomes interesting. I usually call that post war, but I think it really started before the war. For simplicity, I say post WWII.
I think Ueshiba's art of Aikido really can be seen, or thought of, as distinctly different than Daito ryu. And, it can be seen, or thought of, as very, very similar to DR.
Similar first. Techniques are similar, although I'd have to say DR has more. Aiki is similar, although I'd argue Ueshiba never taught all he knew in that area. The outlook of the art is defensive in nature is shared between DR and Aikido. The manner in which Ueshiba and other DR greats show their skill is similar (think push tests, etc.)
Different. The core area where they diverge is how the application of aiki is used. DR takes, IMO, aiki and applies it in techniques to capture center on contact, then quickly finish the encounter. Quite a bit of uke's landing at the feet of nage/tori and locks/blows/etc. Ueshiba changed that to a pass through model. Instead of dealing with quite a bit of jujutsu level techniques, he pared things down so that he could concentrate on ukemi. No, not rolling and falling. His version of ukemi, IMO, was pure aiki. I think that is where Ueshiba diverged from DR in a unique manner. Ueshiba was concentrating on ukemi purely as a way to be the avatar of the kami. That was his "correct" usage of ukemi. Taking all the incoming attacks/energy and changing it in his body so that he could use it in a manner that suited his spirituality. I think he may have gotten a natural high from aiki ukemi.
(aiki ukemi is sort of redundant. I just use it to emphasize the point.)
You can't be a bridge between heaven and earth, be an avatar of the kami, if you're just dispatching uke at your feet quickly and decisively. In that manner, I think DR and Aikido are polar opposites. The former captures in and down decisively while the latter appropriately redirects and sends forth.
That doesn't mean DR doesn't do that (pass through/redirect uke outwards/etc). I'm sure there are aspects where it does. It just means DR doesn't focus solely upon that aspect in the spiritual manner that Ueshiba worked.