The optimal approach for you depends on several factors: the importance of UX to your product and brand, your budget, and your risk tolerance. Choosing a cheap service may not adequately address all your use cases or align with your product strategy. In my professional experience, these services often require redoing later on because they fail to consider your complete business needs.

If you are operating a growing business in a high-demand and high-expectation market, it may be more advantageous to have an in-house UX professional. This can be in the form of a full-time employee or a contractor.

For startups, offering equity to early designers can be a compelling incentive, tying their commitment to the overall growth of the company.