The Plus model is a no-brainer. The price difference is very small.
With the now public key-gen you can upgrade the bandwidth to 3.2GHz and activate all options.
If you then dare a cross-flash, you will effectively transform the Siglent SSA3021X-P into a Siglent SVA3032.
While the corss-flash can, in theory, be made impossible to the common user by Siglent, they cannot change the fact that the key-gen exists, unless they upgrade all users, which would be a major problem for all involved.
But beware that the SVA capabilities are not that great (comparable to a a NanoVNA?) nor are the demodulation capabilities (get a dedicated field meter if you need heigher stream rates). It's nice to have, but with limited usability, in my opinion.
Regards,
Vitor