[frostmatthew]

My first job as a developer was at a very small infosec non-profit (5 employees total!), I now work for a fairly large tech company (VMware) - and while I was in school I worked tech support at a startup that grew from ~30 to ~80 employees in the year and a half I was there.

So I've seen a decent range and think that you'll learn a lot wherever you are (particularly early in your career). What you learn will vary a bit and you will most likely prefer one or the other, but until you've tried both I wouldn't worry too much about which is better. I'd suggest pursuing opportunities at companies of all sizes and accept the offer that most interests you.