I'd say the huge difference is the start menu. Really.
I would keep windows 7.
Not because their is any problem with the software, I just would have it more simple., even though I have a windows 8 computer...
Also, some apps and games do NOT run on windows 8 or 8.1. If you're only considering upgrading to Win 8 because of Micro$oft support, don't do it. Save yourself from headaches and actually using the support several times per day. Other than major bugs, Windows 8 is an okay operating system...just not an upgrade from windows 7.
Hope this helps you.