Ok, the only real thing I can think to easily compare is the total space they give out for free.
* Gmail: 2.5GB
* Yahoo: 1.0GB
While I'll never approach either in the near future, it's definitely something that I wonder about for both companies. Given the current state of technology and the funds that are going into both, is it really the case that every single user could have the full quota? Or is this like the time I was in Computer Science as a student and they gave all of us something like 120% of the total, so when 90% of the people almost hit quota no one could spawn files or make new entries into existing files.