How do you prioritize features at the MVP+ stage?

Building http://ribbon.cool with my co-founder (he's non-tech).

We have a few interested companies/customers of vastly different size. Each one has a different set of needs in terms of features they want/need. For example, a recent feature I developed was to add team accounts. Previously, just for the initial MVP each login = 1 account. For companies to properly use Ribbon they wanted linked team accounts. Developing that feature was a no brainer, we just didn't do it initially as we wanted to prove out the idea/concept first.

Not all features are as clear cut as that though. How do you prioritize which features to build? Which customers are the ones you listen to most closely?