No, learning to lose is part of Iwama weapons as well. There is a continuum, with the "learning to lose" on one end and "awase" on the other - different versions of aikiken and aikijo fall differently on this line, with Saito-sensei more on the awase and Chiba Kazuo, for example, more on the "learning to lose."
As for Kashima Shinto-ryu, there are a lot of videos on YouTube. But the best comparison was the seminar that Stan Prainin organized which had Kashima Shinto-ryu and Saito-sensei on the same stage. I think that video is still available through Aikido Journal. (I will note, however, that it is somewhat difficult to get a real sense of Kashima Shinto-ryu, as the lineage, though not broken, was "wounded" - when the headmaster in, I believe, about 1940, died without fully passing on the school to his successor).
But let me go into a little detail with some things I see in aikiken. First is the micro-detail. Did you know that swords were not to be too sharp before battle. A beautifully sharpened sword tended to slip instead of cut the armor cords, which were made out of silk. So, before a battle, many ryu taught that one cut several times into a "trough" of sand, to make a serrated edge. There are myriads of teachings in each ryu that are certainly not part of aikiken. Without these small details, of course, one doesn't have a combative art, any more that a soldier given a rifle that he doesn't know how to clean and maintain has learned gunnery.
But let's look at the macro-level
. First of all, that's not cutting with a sword - they are snapping out their arms. Beautifully, crisply, but it's not kenjutsu. But a larger problem (from the classical perspective) is this - for 600+ years, uketachi in classical ryu was the teacher. The teacher creates the conditions, with his/her body for shitachi (tori) to learn. As shitachi improves, uketachi raises the bar. Ueshiba flipped this over (as did Takeda) - when the teacher is the winner, it is significant. The teacher may be demonstrating a principle (and I believe that's so), but the student will not learn the subtlties of combative engagement (and the result is, as far as I can see, that Ueshiba was better than Saito Morihiro who was better than Saito Hitohiro who is better than his students). You have essence of a teaching model throughout Japanese combative history, geared to enable students to surpass the teacher --abandoned by aikido. (I don't like repeating myself - I wrote an entire book on the essence of koryu in Old School and fifty plus pages on this history and substance of aikiken in HIPS). So that's enough detail on that - those interested enough in more of my thoughts on the subject are welcome to read them there.
But I would like to take on one more topic as illustration.
Yakumaru-ha Jigen-ryu Yokogiuchi
Many people think this looks and sounds utterly bizarre (interestingly the kiai is almost exactly the same as the infamous 'rebel yell' of the American Civil war). Aside from the incredible body organization, note that the exponent hits exactly the same point on the bundle of sticks, an embodiment of the principle of tombo no kurai (dragonfly on a post - NOTE: I wrote a lot on this on e-budo years ago. If it's archived, I'll put it on my blog).
Here is Ueshiba and Saito
Because they've made a two-person form out of the practice, it's not strictly the same, but Ueshiba and even more Saito are shoulder dominant in their strikes. As Ueshiba always said when "stealing" another ryu's techniques, "in aiki, we do it this way." There are a number of essential principles of Jigen-ryu that he is ignoring, does not know, or finds irrelevant to his training. And Jigen-ryu was the essence of aggressive sword. But more than that - and in other films I've seen of Ueshiba, he doesn't hit the same point on the bundle of sticks. That's the essential teaching of this training! - He makes it a physical exercise rather than a very particular kenjutsu exercise (again, tombo no kurai - "a dragonfly always lands on the post, no matter how he flies" - this being the epitome of ma-ai training).
I couldn't quickly find Saito sensei's tire tanren-uchi
, but this example will suffice. It is my understanding that the tire replaced the stick bundles, because they don't wear out. But they are really different (I've trained this way myself). The tire bounces back, whereas the sticks absorb. The latter encourages cutting power. With the tire, the shock is reflected back into the body, even to the degree of creating damage - distortions in posture, particularly the hips. To absorb it, one tends to stiffen. Furthermore, most kenjutsu grips in such a way that the web of the thumb/finger is at the top of the tsuka. This is not a problem because one cuts - one draws the sword along it's length. But tanren-uchi, (which will build a really strong body!) strikes the tire, and therefore, one is taught to "cap" the tsuka with the fore-finger knuckle. This protects the hand and thumb from repetitive stress injuries, but also tends to raise the right shoulder and lock the shoulders forward (Note Saito Hitohiro for a more extreme example of this
I could continue, but this is just a little of what I see. The result is not an assertion that aikiken is inferior. I'm saying it is essentially different. Note that in my essay I recommend a study of a koryu - this is one reason why...so one can actually know the differences from the inside.