Ask HN: Advice for considering proposals for outsourced software development

I have been asked to review a set of 10 software proposals to create a product for a founder. This is my first time doing such a task, what questions should I be asking of the proposals in order to identify the better ones out of the bunch?

Obviously I can differentiate based on the size of the teams offered and the time frames they propose, some also clearly have more consideration for the UX design of the product than others. Any advice or experiences offered would be much appreciated. Thanks in advance.