Very good post. I think times have changed quite a bit. Similar to you, coming out of a CS undergrad I only considered huge (20,000+?) firms. Most of my peers were similar. 1 or 2 went to the 50 person shops, and were considered visionaries. What's changed is people realize that bigger firms don't like to change, so you get locked in to old technologies. They also offer less career alternatives - the top spots are all filled. So there's much less downside to joining a firm that may go out of business. (Look at Blackberry as the counter-example)
There's just one thing that you missed - mentorship. The first job does disproportionately put someone on a career trajectory based on how they learn to operate. 10 years later, your first boss will have a higher impact on your career than your undergrad degree. This means that it is more important to pick the right first manager at a startup, then getting the firm right. Finding a boss whom you respect, that will give you time is the most important thing for a new grad.
That's a great heuristic. Reminds me of Keith Rabois's advice: select an early stage startup by evaluating who your manager will be.
"If your manager is stellar, at a minimum, you will learn and stretch your abilities. Moreover, if your manager is an outstanding engineer or director of something or first-class entrepreneur, he will have many exciting opportunities in next 1–10 years and if you are talented and display an outstanding work ethic he will be begging you to join him at his next endeavor."
That's exactly it. Learning is what's most important that early in a career. Long term career earnings dwarf year 1 or year 2 salary. It's also rare for an undergrad to make retirement money in short term options right out of school. It happens, but it shouldn't be banked on.
There's just one thing that you missed - mentorship. The first job does disproportionately put someone on a career trajectory based on how they learn to operate. 10 years later, your first boss will have a higher impact on your career than your undergrad degree. This means that it is more important to pick the right first manager at a startup, then getting the firm right. Finding a boss whom you respect, that will give you time is the most important thing for a new grad.