On high level technique......
I have felt high level technique from many, most obviously Takamura sensei but this also includes several top notch Daito ryu shihan, aikido shihan. Don Angier, Ushiro Kenji, Tetsuzan Kuroda, Mikhail Ryabko, Vladimir Vasiliev etc...
Is it all the same? No. Each manifest their advanced application of waza in different in way. Kuroda takes your center immediately with a very soft touch. It's like an encounter with a ghost and unlike what I've felt from anyone in Daito ryu. I'm not saying its necessarily better, but it is distinctly different. Laying hands on Ushiro Kenji feels like grabbing a gorilla. ( Okay you got him, what are you going to do with him?) All the others are great, each in their unique way. My point is that people often become fixated on what "they" consider high level. If you like X-ryu okuden-aiki-myoden-voodoo, good for you, go do it. However, don't dismiss everything else thats different out of hand. Keep an open mind and realize you'll never learn it all. Myopic evaluation of others is intellectual failure and the stuff of defeat.
I agree to keep an open mind and not to dismiss things that are different.
But, I do think that the answer to the question you wrote, "Is it all the same?" would be a yes and a no. You answered "no" in that the people quoted handled the "application" of waza differently. I think most of us would have a hard time arguing that.
It's the "yes" part of the answer that tends to draw debate. I haven't had nearly the experiences of working with as many people as you have listed, and I'm a beginner at this aiki stuff ... however I've been able to work with both Mike Sigman and Dan Harden.
Two completely different applicational usages of these skills. Which makes it even more disconcerting when I'm listening to Mike teach and he says nearly the exact thing Dan has said. Double disconcerting when I'm listening to Dan and he's saying nearly the same thing that Mike has said.
How people use these skills -- very different. The base/core skill itself? I think that it's very close to being the same, if not the same. The training methods sometimes vary, but then again, sometimes they are scarily close to being the exact same thing.
And a couple of days ago, I talked with someone about training and how waza/jujutsu/etc factored into skill advancement. The person I was talking to mentioned a correlation between training in jujutsu type stuff and just training core body skills. Long story short ... the idea is -- What if waza is detrimental to building core body skills?
If you're using waza to build these skills, it's the long road. If it's a road at all. But, if you're building these skills and then working primarily in waza to use them ... will you get better? Wasn't it Sagawa that shut down his dojo just to work on solo exercises? Did he come to this realization?
I can look at someone who is doing solo exercises and paired partner work to build this skill and in 3-5 years, they are very strong (in the budo sense, not in the physical sense). If at 10-15, they start doing waza 75% of the time, then just how much core skill are they building compared to say, doing waza only 25% of the time with the rest focused on core body skills? It really makes you wonder just how much is in "waza" and how much is in core conditioning. Does waza impair the advancement of skill?