Should I install vim or GVim ?
I develop mainly Ruby on Rails (I also use IDE's, but different topic).
Are there any differences or advantage of using Gvim vs vim ?
In gVim you can select the font, vim depends on the font the terminal provides. And it's the same for colour support. Gvim has full support, vim depends on the terminal.
Gvim additionally has menus and a toolbar, which vim lacks.
One big advantage of vim is that, since it's a terminal application, you have a full fledged terminal at your fingertips. gVim has very rudimentary terminal support. This is handy if you run
:make, for instance.
Install both and try them both, they use the same configuration etc. so there's no risk.
As far as differences are concerned: one is a graphical tool one is a command line tool. So the advantage of vim to gvim is that you can use it easily over an ssh connection. (You can do the same with gvim by tunneling X but that has quite some overhead.
gvim package shall have all vim coming along. Meaning, if you wish to fall back to vanilla vim you can.
Anyway, the biggest difference IMO is that vim depends on the terminal to handle special characters and key-sequences. If you wish to map and exploit things like
<m-ins>, ... just forget about it with vim.
Of course gvim has menus, mouse, toolbar, etc. But that's just a small bonus compared to a fully functional keyboard.
They both are the same if you see performance wise but if you want good looks and want to customize the editor so that it does not look boring then you would like to try the enhanced version of vim.
For me, the biggest disadvantage to using gvim over vim is that you can't run it inside a detachable container. I run vim inside tmux, which allows me to detach the running session and reattach it later. For example, I can detach my session at work, go home, ssh in to work, and reattach to the already-running session. I also do a lot of work on remote VPS hosts, which makes the ability to reattach more important, since I might lose my ssh connection. Gvim is appealing to new vim users, and it's a nice way to get started, but once you're a vim power user, menus and other GUI elements just slow you down. Vim can be configured to use a mouse in terminal mode (even over SSH), and if you set your terminal to use 256 colors and a nice Unicode font, you can get pretty fancy without the overhead of a GUI.