I'd say Dickinson has better gap control, passing, more accurate shooting, and is smarter than Silayev
I don't agree with gap control, if there's anything Silayev can do its control gaps. He's almost Chara like at his age, and doing it against men.
Dickinson does have a better shot, through and through, but as a D, the transferable skill is getting pucks on net, and I find Silayev does it better than most D's in this class, and certainly Dickinson. With that said, Dickinson has a better vision and more confidence to open up lanes in the offensive zone, so it's not something that is a big difference between the two. I find Silayevs vision to be to notch actually. It's sad I haven't scouted him more in years prior because I haven't seen the progression like per say with Iginla, but I'm sure his progression has been massive.
Dickinson is a better zone defender, I'll say so. I think that (And shot strength) it's probably the easiest thing to teach generally in the NHL, that's why almost anyone that's willing can play the PK.
Dickinson is more polished, thus has better shooting mechanics, better activation (Unclear whether that gets better for Silayev, but there's a chance, right?), better zone defense and he's also a more precise passer, but generally, the things that tend to get better with age are the things that "lack" on Silayevs part.
Also Silayev is a good puckhandler, IMO better than Dickinson, non-negligible as an offensive D. It's the reason why Matheson isn't a bonafide 1D. (Well that and the fact he's r-rated.)