It's a healthy balance of both. We do smaller, qualitative user feedback sessions mostly internally -- especially with customers who are in beta programs for our new features.
But broader market research initiatives that require greater scale, we often bring on great partners like Forrester, YouGov, Suzy, and other survey/analytics tools to get us the level of responses we need.
It always starts with the business objective, and then moves into user needs. What I find is that happy, satisfied customers most often move the business forward. So, I like to start with a long-arch view of what we are trying to achieve, quickly followed by what we hope our users will say / feel when using our product. If we can align on those two objectives and the time horizon, then market research is usually a great tool to help us work backward and figure out what steps it will take for us to create that experiecne for the customer.
Think about where the bigger pain is for your organization. In product marketing lack of resources is usually the case, so you need to prioritize based on the needs of the company. you have major issues with churn I'd suggest starting with user personas, on the other hand, if sales are struggling to close deals, the buyer personas should be your priority.