I've read in https://docops.ca.com/ca-spectrum/10-2/en/installing-and-upgrading/install-ca-spectrum/installing-ca-spectrum that you don't get Huge Landscape support if you migrate/upgrade to 10.2 rather. It requires a fresh install. I assume that means that the added value of having a 64-bit architecture is diminished greatly.
Are there other features which are impacted by upgrading rather than installing? Does this include upgrading by means of taking the SSDB and installing on a brand new virtual machine?
I wouldn't say that you will lose an improvement if you upgrade. It is similar when you have Windows 32 bits and you wish 64 bits. You cannot perform the upgrade, only with a fresh install you will achieve that.If you are planing to have more than a million of models in a landscape, then Huge Landscape is required. If not, you can perform the upgrade and remain in a regular landscape.
Can you think of another feature which requires a clean install?
Nothing that comes to my mind.