yeah that's a good question. from what i've seen/heard, a few things stand out:
* first, their actual expertise. some firms just say they do AI but don't have deep knowledge in specific areas (like vision vs nlp).
* then, their past work. do they have real case studies or just talk a good game?
* also, how they communicate and integrate with your team. some just hand over a solution, others actually help you build capacity.
* oh, and cultural fit too. really helps if you can actually work with their people.
