Yes. I would say the similarities lie in the fact that one needs a willing participant for most of the techniques to work. I do believe that some of the wristlocks, etc., from Aikido can absolutely work in the right circumstances, but most of the vids I have seen are from guys flopping around willingly. Same with Systema, but I have never seen anything useful from Sytema.
Disclaimer: I have no real world experience with this stuff. I just watch a lot of combat sports crap.
I don't have a dog in the Systema fight, but on the subject of aikido and the "willing participants" you see "flopping around," that
is a misleading aspect of aikido, but it
also is straightforward and practical: To facilitate drilling, they teach you how to fall and roll in such a way that you're going with the technique. It's like pro wrestling bumps, a specific way to fall and get back up to keep the momentum going and to keep you safe so you can keep training.
The problem is that it's hard for noobs to separate fact and fiction. For example, in a real fight, nobody who gets their wrist bent is going to do a 360 flip in the air.
That's not what that technique would actually look like if applied to an actual attacker. They would just slowly crumble to the ground or they would roll out of it the way that you roll with heel hooks and toe holds. I experienced this as a kid when I was training in aikido and then would fight with my friends. I was friends with wrestlers and generally athletic kids, and when I'd do aikido techniques, they'd intuitively go with the wrist locks, and so I had to get good at going from one technique to another just like going from a heel hook to a kneebar. I also got better with my leverage to where I could bring them to the ground before they could spin out of a given wrist lock. Sadly, that sort of "real-world" experience wasn't something that I ever experienced in my aikido classes. But acknowledging the fact that the falling and rolling in aikido is intended for drilling purposes isn't to deny the effectiveness of a lot of the techniques.
For a cool - and the most "real" and least Bullshido-ish - look at aikido training, I've always loved this Seagal documentary. Hagiography aside, it's cool to see what his dojos were actually like, how he'd have them do the randori and let them just fuck each other up in as raw a fashion as you'll ever see in any TMA gym.
The most interesting parts are 13:42-16:20, 25:33-27:48, and 43:01-48:00, with Seagal teaching classes. The best part about aikido is the randori, but the worst part is that the randori is often so sanitized and reduced from a chaotic battle to something closer to dancing or synchronized swimming. I quit aikido as a kid because we did a randori exercise with some black belt who our sensei made a big deal was from Japan, and during the exercise, I shot a double leg and took her down and my sensei stopped things and told me that I wasn't allowed to do that. I knew enough even then to know that the whole point of the randori is that there's nothing you can't do, and I also knew that if a black belt couldn't stop a double leg from a 12 year old then the black belt was meaningless. That was it for me with aikido. But if I trained at a place that taught realistic aikido, not the cooperative BS that has sadly so polluted the art that
that's what it's known as, I probably would've kept at it for a long time.
