The question you should always start with is: “What do I want to learn and why?” By identifying what you want to learn and why, you can select methodologies that support your team, users, and your long-term goals for success.
Time and money are obvious factors here—but there can be multiple methods that help you achieve a goal. One option could be scrappy if you’re tight on budget and the results don’t necessarily need to be watertight. One option could be more in-depth and extensive for answers you really need to rely on. It’s all about what you want, need, and can invest in learning.