.... I don't (as yet) notice a real speed increase or decrease. Possibly, if I had uninstalled ver 8 and done a clean install of ver 9.1, I would have seen a speed up since ONLY new installs (not upgrades) install SQL Express 2012 x64. And why is this ?!!
Because this requires either a full uninstall, including SQL, or someone manually doing the SQL uninstall, reinstall.
The slowest part of the install is when it looks for upgrades/patches - that can take 1-90 minutes right there.