I can't really speak for the hiring managers. BUT, from a senior developer's perspective I'd honestly be more interested in software you built that other people use...

IE... packages or libraries you maintain demonstrating how others have shown interest in how you provide a correct and maintained solution to a common problem. (Because that's the core job of any developer) Projects can showcase that as well, but are better at showing other things such as how you approach common and uncommon problems in an overall perspective including the user experience.

So to summarize, demonstrate not only the "macro" but also the "micro" aspects of development.