Specifically in regards to cofounders, the math is different. The founders will drive the direction of the culture of the business going forward, so a bad attitude will likely yield poor results in the long run RE: retention etc.
I'm speaking moreso from the perspective of a manager in a larger org. It depends on the context of course, but working with junior or less capable people can turn into a micromanaging by necessity kind of situation.
e.g. need to be very specific about design/implementation details when providing direction. Versus somebody who is highly competent, you can generally just give a high level direction and leave it to them to fill in the blanks.
The goal is never to micromanage, obviously, but if you have a lots of design decisions to make, it can be necessary to have tight control over those decisions to maintain quality. This situation can become draining to manage.
This is where formal processes and agile etc become important. But if you have a team of all highly capable and motivated people, you can have much looser processes and yield better results. Don't need to specify every detail of every task up front.
I'm approaching this as a manager who is more heavily involved in the technical side... but in other situations, it might be the tech lead doing these things.
But I'd for sure take somebody who's friendly and nice to work with over a highly competent but abrasive person. There's a middle ground there...