The difference between MITs fall and spring career fair is night and day. For the fall career fair, there's usually a long line to the gym (most of the gym is used) if you don't get there early (or go later in the day but risk recruiters being tired). The spring career fair is much smaller and if I remember correctly it is mostly comprised of research based opportunities. There isn't much presence from SV software/tech companies. I think the fall career fair is about an order of magnitude larger than the spring one.
I wouldn't say an order of magnitude, probably about 3 times the size.
As a former student and then recruiter for the SV company types, the Spring career fair was pretty good at filling up the intern roster. Definitely the fall is much much better for full-time & junior candidates.
