Shinki is shinki, that's the point: shinki is the product of a single tannery, therefore Aero shinki is SB shinki is Buzz Rickson shinki is Good Wear shinki ad nausea. As far as I can tell, only the likes of Buzz Rickson and perhaps Good Wear are able to specify to any extent the grain and finish of shinki hides - the rest of the makers have to take what they are given, which is probably what GW and BR are stipulating.
So therefore ... all Shinki is NOT the same ... I equally know that Shinki have "grades" of leather like most tanneries and therefore must produce multiple finishes - they certainly produce shell cordovan for the footwear market which you would be very unlikely to make a jacket out of ... I don't know the "grades" or "finishes" they produce but I'm sure you could google it to find out. I know from pricing it up a few years ago it's certainly not cheap ... but also not as expensive as you'd think. I remember getting a sample of the Aero Shinki some years ago and I thought it was really good ( it had quite a shiny topcoat ). The SB Shinki seems duller by comparison, very A2 like, it's certainly not plastiky .
The Clayton is smoother ( less grainy ) and the grain is more subtle. It appears slightly deeper in both colour and thickness and is of a slightly softer hand.
SB's Blattenwerk HH is also pretty impressive stuff ( very grainy) .. but was a little too heavy for what I wanted in a CR ... but if heavy Horween CXL is your bag then this is nicer IMHO.
HTH