Compare between Windows 7 vs windows 8 vs windows 8.1 , advantage and disadvantage and tips and tricks you know ?

Sir, There is a long list to discuss on 

One of the main advantage i want to discuss is about "Cloud"

Any thing you want to do can be done through CLOUD.

And One main Disadvantage is-

Lots of unwanted  Apps running at the background  which is not possible for the general users to handle, resulting in the consumption of memory.