I've had trouble with the completion plugins for Vim. There'd be a "completion engine" that needed a language-specific "plugin" and I had trouble getting those + dependencies working in various environments (or they'd suck down CPU resources). Maybe if I just set it up once in one place it'd work fine. It might just be me since the CPU resource suck bothers me in other IDEs like PyCharm.

I really like the out of the box completion vim has where it completes against words in files you have open. Most of the completion I need is long variable names or functions/modules and if it's not in the same file I'm editing I already had it open in another buffer.

That and a basic PEP8 linter work just as well for me as any of the major IDEs I've used.