Interesting question, at the time the S1 chassis was hyped up to be really something quite special, similar architecture to the V8 Vantage except it was bonded and riveted, not just bonded.
Interestingly when Aston sold off the chassis/architecture rights to the old Vantage platform it went to an anonymous bidder, reported to be Morgan at the time as it co-incided with a lot of their timelines, any truth in this - absolutely no idea, but if true it would be interesting as to what they used in the CX platform, if anything.
I have driven a Plus Four and it did seem nice, but I can't say I felt on a quick b-road blast that the chassis was better or worse, it felt very similar just quicker steering as my S1 has the original power steering and is pretty heavy. They report how much stiffer it is, but the Aero is pretty stiff - so much so it had no rollbars, so I can't tell what they are referring to exactly as often its in the finer details with marketing blurb..
Either way, both will be great choices.
