This is a question asked many times by beginner programmers, if they should focus their efforts on another language in the middle of learning one. It's really a trick question since learning the concepts of computer science isn't about the syntax of your code, but about the concepts you take away with it.
So you can take a peek at both languages, check their documentations and see which one speaks to you more, see which self-learning courses make more sense to you. Then see it through and challenge yourself with projects. These projects don't even need to be anything new. Just program more and more. The rest will come to you, and other languages will be second nature since they all use the same concepts.
TL;DR: Python.