A nice way to compare two (or more) files on different servers with
vimdiff - which is just an alias for
vim -d file1 file2 filex - works like that:
$> vimdiff scp://remotehost//path/to/file1 scp://remotehost//path/to/file2 scp://remotehost//path/to/file3
Of course you can also compare files on localhost:
$> vimdiff ./file1 scp://remotehost//path/to/file2 scp://remotehost//path/to/file3
Actually vimdiff is also a great difftool in tandem with
git and other (D)VCS when you like to use the command line a lot.