Any style that teaches its students to hit the floor safely has a lot going for it, I don’t want anyone to think that I have anything against Aikido, but I am a Taijiquan teacher, so my bias is obvious, even to me!
My statement above was solicited as an opinion and presented by me as such (as is everything below), not unequivocal eternal truth. But, so you don’t think that it is entirely blind faith, I should explain where the opinion comes from.
I have two and have had three Aikido black belts from two different styles among my students. I have worked with them and other Aikido students for many years, indeed, for my entire career in Wu style Taijiquan we have had former (and some current) Aikido teachers and students in our school.
Technique-wise, I agree that there are some similarities in principles. Aikido’s locks and throws seem to rely very much (IMO) on a motion quite similar to the “split” power generation lie (, liè), a spiral twist using various size circles in a varying angles of diagonal or horizontal planes relative to the momentum of the opponent. This has the effect of automatically rolling one’s partner along to the ground as they fall, with the degree of relative roll determined by the thrower. It fits very well with the desire not to hurt the opponent, and it is only when performed improperly (usually by accident) that people get hurt in training, IME. Indeed, the Taijiquan that I have learned is one third traditional Chinese medicine, and the Aikido people who come to us have done so when they were hurt this way. They have told me, anecdotally, that there was no provision in their former schools for the injuries they sustained, and it was even recommended once or twice by their teachers that they come to us. Conversely, I had another Aikido black belt get into quite a bit of hot water with her sensei for coming to me for treatment without his prior permission, for the (to my mind justifiable) reasons I set out in the paragraphs below.
As a teacher, if one of my students were to ask me (or tell me!) about concurrently training in another school, I would automatically assume at first that I had failed them as a teacher, by not giving them enough to keep them busy learning and growing in the art. If, after having gone through my entire history with them to see if indeed I had left anything out, I could see that I hadn’t and they did go to another school, I would be done with them. The Taijiquan we’ve inherited is many lifetimes worth of study, and to mix metaphors, unless it was an extremely fortuitous circumstance (there is some precedent for advanced students of our teachers cross-training with exceptional teachers from other styles) impairs that transmission and limits the student’s opportunity to work to their full potential.
There is only so much time in one life, there are only so many students one teacher can teach, if thay have an art worth preserving. I am on the lookout (“like a tiger” as the I Ching says) for students who can make the most of my limited time on this earth, as my teachers were when I met them. Many people disagree with this approach, and that is OK, I don’t have to teach them either.
I hope this helps to explain why I wrote what I did.