The Python plugin for IntelliJ is virtually the same as PyCharm. The plugin sometimes lags a bit behind the PyCharm version, while PyCharm sometimes lags a bit behind the IntelliJ IDE version, but in general, it's the same.
Of course, you get support for lots of other languages in IntelliJ that aren't available in PyCharm.
It's mostly the support for other languages and plug-ins, to be fair. For example, I have to write cucumber-style BDD tests for my Python projects sometimes, and I use the Behave framework for that. IntelliJ comes with a nice Behave plugin that allows me to ctrl+click on the step in the .feature file and it takes me straight to the Python code with the relevant step definition. This plugin is not available for PyCharm, for some reason.
