What is the advantage of Ubuntu over other Linux distros?
Ubuntu has no advantage over other Linux distro but since most distros are based on Ubuntu that's why everyone recommend Ubuntu. I personally don't like to use Ubuntu as its interface it too fancy for me and that's why I use derivatives like Lubuntu which is a cut down version of Ubuntu for low end systems and it works smoothly on high end systems as well.
The difference between Lubuntu and Ubuntu is the desktop environment, the Ubuntu uses Gnome as its desktop environment while Lubuntu uses LXQt as its desktop environment. You can install same applications on both of those distros but I would still go with Lubuntu as it's interface is easy and it runs pretty fast.
You can also check also distros which are designed to do specific tasks. I prefer you to try Puppy Linux that's one of the fastest distros out there and it loads directedly into the ram. Just 300 MB in size but a good one. You can also try Ubuntu Mate as that one is also a good distro with Mate desktop environment. The Ubuntu Mate works like a charm on my old Raspberry pi 3B and it works similarly on my old laptop.