Upgrade VS clean install

OK Chelidze - - - here is your answer. The PC's (laptops and desktops) will run at least as fast, and perhaps slightly faster. But that depends to a great degree, on error free upgrades. The upgrade process in some ways is easier than a full re-install from a new ISO device (dvd or usb-flashstick), but not as reliable.

For instance, to upgrade from 14.04 to 16.04 . . . it's best to clean up the 14.04 PC's so they do not have any PPA's or unofficial sources enabled. And to make the OS's as "vanilla" (plain/basic) as possible. And to make 100% sure they are completely 100% updated with zero updates pending. And to make sure you have very reliable power source. And very, very, very reliable inteet source (wired best, but wireless OK if it's 100% stable). really, when I think about it, this is also true of all versions past 14.04 - - the same principles apply for each version.

Personally, I think a new install is easier on the front-end but a little more work on the back-end (add media codecs and other cutomizations).

Hope this clarifies your conces.

PS . . . I just noticied DeadFlowrs response above - - that's even better advice - - as it takes 3-6 months for an LTS release to remove all the various things not working correctly (for production PC's - - hobbyist PC's not such a big deal)