I've applied for senior jobs where the interviewer was very impressed with my side projects but chose not to hire me anyway. For the most part, they didn't seem to care about the other things as well - the fact I consulted for a tech giant the size of Google, or taught certifications, or architected a project with millions of daily users, or rewrote a year old social media app from Cordova to native iOS+Android in two months with a 3 person mobile team.
The decision seems to fall to the default, "What's the O(n) of a Set" or, "Tell me what you worked on recently." You could probably build an operating system or Dwarf Fortress as a side project, and they might not even notice it.
I'd say just pick whatever showcases you best as a person, and it will catch the eye of someone who's looking for a person like you. I ended up getting a job doing research, where I get to quickly hack together lots of prototypes, so it's a perfect fit.
The decision seems to fall to the default, "What's the O(n) of a Set" or, "Tell me what you worked on recently." You could probably build an operating system or Dwarf Fortress as a side project, and they might not even notice it.
I'd say just pick whatever showcases you best as a person, and it will catch the eye of someone who's looking for a person like you. I ended up getting a job doing research, where I get to quickly hack together lots of prototypes, so it's a perfect fit.