Since these firms charge a % of the deal they have an incentive to get higher valuations. It also looks good on their resume. But you can just look at their por

Since these firms charge a % of the deal they have an incentive to get higher valuations. It also looks good on their resume. But you can just look at their portfolio and see the exists they worked on, the valuation, who the acquirer was, etc. You can try and reach out to some founders to check if they liked working with the advisor too.