At least I would never run again one of the migration scripts (Parallels <> VMware) or even upgrade scripts between different Parallels versions again (I had an one year adventure with VMware). Even not for testing purposes.
IMHO it is more time-consuming to fix the glitches and issues because of these scripts than to setup a new Mickysoft system.
Now the new version of VMware Fusion has been released too. I'll have to find out which product will support the iMac best.
Yeah, I guess that it'll be faster. However, 50 % faster? Sure, for certain, very specific tasks. I think it's much like the fuel consumption numbers that car manufacturers promise (no wind, hill down, new road, constant speed etc.).
Nevertheless, at one moment I'll upgrade of course ;).
Desktop 10 has been faster than version 9, so this might be possible. But it is indeed a pity that you need to update, at least if you want to keep up with OS X updates.
Hans CafeTran Wiki
Parallels Desktop 11: 50 % faster again? Too good to be true?
It's a pity that they always demand so much money for their annual updates.
I've also understood that it's possible to upgrade a VM with Windows 8.1 to Windows 10. Didn't dare to do it yet.