Questions like this don't accomplish much. That's why talking about this stuff is almost impossible in my opinion. Its difficult to agree on technical parameters that aren't hobbled by semantics. You've got to get your hands on people.
I'd have to go with Rob on this one, questions like that can accomplish something.
Every time someone says that technical parameters are hobbled by semantics, I think back to my initial encounter with Mike here on Aikiweb. Both of us come from completely different backgrounds, but we were able to establish a common ground that was pretty damn obvious that we were talking in the same direction.
(I think someone at the time was calling me a twat for saying that power could be "generated" from the ground)
In my own personal experience I've found most that have a SOLID understanding of these skills have little trouble making headway with those kind of questions.
From my own contact with Systema, I'd also have to say that they have elements, but there are some crucial methods of using the body that they do not use.
For clarification, I don't mean that makes internals superior, but that Systema simply doesn't necessarily make use of the same things, although there is inevitably some overlap.
There's a couple people I know that have close hands on experience with Vlad and Ryabko, having trained for a good deal in Systema, and also studies under Ark.
It's always interesting to hear their comparisons, about the difference in feel between the three, not to mention the utilization, or rather non utilization of certain body mechanics.
Whether A or B is superior etc...well that's really a matter of taste that can only be made once you have a basic grasp of skills on both sides.