Looks like they are just making 1 device, but in a few flash / RAM sizes, then putting it out in a few dofferemt packages.
Hence they all seem to have the same number of timers etc, but some have more GPIO because they are in a larger package. I suspect the same applies to external RAM support in that its in all of the cores but not connected on some packages.
RAM and flash size variations my be a function of the manufacturing process.
I suppose in the end, it just comes down to pricing and whether anyone makes affordable / cost effective boards based on this device