The two advantages of using Python for me are being able to use utilities I've already written, and the comprehensive standard library.
For example, I wrote a macro to split long Python function calls into multiple lines, and I could access a parsing function that I already wrote, along with Python's own compile() to detect when I've parsed a complete expression (yes, this one is Python-specific).
I also wrote a macro to submit the current file to a private pastebin, and AFAIK you can't make web requests with Vimscript.
For example, I wrote a macro to split long Python function calls into multiple lines, and I could access a parsing function that I already wrote, along with Python's own compile() to detect when I've parsed a complete expression (yes, this one is Python-specific).
I also wrote a macro to submit the current file to a private pastebin, and AFAIK you can't make web requests with Vimscript.