There isn't just one thing that we go by when hiring. Yes how the individual fits into the team is one of the biggest factors. But where they worked and what experience they have is also a very big factor as well. It also depends on what role we are trying to fill. If a senior developer has just gotten done and we really need to replace them we wouldn't hire some one with out a lot of experience. But if the need wasn't immediate we would probably take some one with no experience and train them.
I guess what I am saying is that there are a varying degree of what people look at when hiring. You can't just blindly say oh this person worked at a start up so they must be a good developer that is passionate about it. Or this person worked at a corporation so they must not be passionate about development.
So when your coworkers tell you that companies look fondly at people that have worked at start ups I would say they are full of it. Some places might do that but it isn't a place that I would want to work at. I would want them to take a much broader look at the candidates and much sure they are getting the right fit for the job.