While i hate the yearly upgrades i have to give real world performance and responsiveness to Parallels 11.
I have always *wanted* to use fusion, as i wouldn't mind installing it on my other machines, but that was more of a 'nice to have' feature; but the performance hit in day to day emails, spreadsheets, (non gaming) related tasks, Parallels has always seemed more fluid even using the retina display, and when comparing Fusion 8 and Parallels 11 on my machine, both VMs with the same specs, i just can't get used to the choppiness that Fusion brings.