Who you pick to be your mentor depends on your needs and preferences. There is no definite answer. But here are a couple of questions for you to consider:
What is the business challenge you're facing? ------------> you can search for mentors with specific skills by using filters on the mentor search page.
Is your challenge answerable by posting a public question like this? -----------> maybe you want to do that if you just want a quick answer.
What kind of mentoring relationship are you looking for? ----------> You'll find different mentors to be valuable based on your needs: short term, long term; specific technical question like marketing, or broader strategic question like business planning
Finally, start the conversation and see if and how you want to develop a relationship with them.