Pycharm has automatic formatting, much better autocompletion (it deduces type based on context), continuous PEP8 check, class hierarchy, refactoring support and a terrific debugger.
Don't get me wrong. I am not trying to bash your choice. I am merely curious how to achieve the similar in vim, because I have some urges to switch as well.
I just use a combination of print statements and pdb for debugging, I don't trust automatic re-factoring for Python though, so I tend to do them manually with regex.
What really helps vim beat PyCharm/IntelliJ for me is the fact that I work with a lot of C code as well as Python. IntelliJ's C support sadly isn't quite there yet.
Don't get me wrong. I am not trying to bash your choice. I am merely curious how to achieve the similar in vim, because I have some urges to switch as well.