I don't actually notice much of a difference between the two, as the end result looks identical. If you use Vim and are switch to Neovim it's an extremely easy 1-minute process. I switched from Vim to Neovim. I can't say I found much of a difference, but the key points where Neovim could be better than just vim is that first, there are much more people maintaining Neovim compared to vim, which means fewer bugs and a modern code base. It also has a smaller code base which might result in a small speed improvement. Another thing is that it's basically just a fork of vim, so what harm can it do? ;)

Neovim can basically do everything Vim can with one major advantage - the number of contributors to the code base is just so much wider (Vim is ~100% maintained only by B. Mooleanaar). Whatever you learn for Neovim you can also apply to Vim and vice versa. And of course there is the never ending Vim vs Emacs controversy - but better not get into that war.