Many people don't like Ubuntu because of Gnome, plus Canonical collects data from Ubuntu by default unless you manually opt out. None of those problems in Mint.
Note that Cinnamon (or MATE) on Linux Mint are based on GTK2, unlike GTK3 for Gnome. Thus, they are compatible with GTK2 themes but don't have the new UI features of Gnome/GTK3.
What exactly you dislike about Gnome. Is it bloat or less functional?
There was a time when KDE used to be cancer (bloated, memory consumption, slow, etc but good looking) while Gnome was the simple and light desktop environment. Today it's the opposite, KDE has become light, fast and responsive while being perhaps the best looking DE while Gnome has become complex and bloated and now features unintuitive UI elements like the three-line menu buttons, etc.
The Gnome team recently adopted the philosophy to become THE standard for Linux UI. The justification is that since there are too many desktop environments with different UI/UX, a standard is necessary. A lot of people don't agree with this, especially since their "standard" has very weird UI elements, radically different from what everyone is used to and unintuitive. Thus, Gnome's popularity has tanked a lot in recent years.
So that means Mint is basically advanced version of Ubuntu?
Not really, they are different projects. Mint is basically modified Ubuntu and it also depends on Ubuntu updates to update itself. So Debian is upstream to Ubuntu while Ubuntu is upstream of Mint.
Cinnamon DE (or MATE) on Mint is trying to keep the same intuitive UI of previous gnome versions and thus forked some popular gnome applications to maintain that look and feel.
I think I would like to remove Ubuntu and upgrade it to Mint, if that's the case.
There isn't anything too different other than the UI and some applications, so other than trying out the distro, there is really no reason to switch. However, if you want to try it out, you could create a Linux Mint live USB to try it.
Distro hopping can be a pain depending on your setup. If you have your /home on a different partition, then it will be easy since you just have to format your / and install the new OS, thus maintaining your home directory and all your files and settings there. Otherwise, you will have to backup your /home everytime you want to install a new OS.