I haven't faced this problem myself, but I have a few friends who've been in somewhat similar situations before. Most were more interested in the smaller company, but due to various reasons (rationalizations?), ended up picking the bigger company job (ibm/microsoft/amazon/google). Despite their stated intentions to only work for a few years to learn how things work in the "real world" and, of course, make some money, they seem to have no real intention of leaving now.<p>At the same time, with the exception of one of the Google people, none of them are particularly interested in the work they're doing. So it seems that earning the big money and having relatively stable, secure, and only slightly challenging jobs becomes a local maximum that is hard to escape from.<p>So while it's true that you'll probably have many jobs over your career and in the end what you choose may not matter as much as you might think, it does seem tougher to go from big company -> small startup than the other way.<p>Another data point (anecdote) about IBM specifically: I know 4 people who work (or have worked) at IBM, on the software-side of things. None of them says that it's very hard. One actually quit because he said it was ridiculous that everyone just constantly slacked off and nothing got done. On the other hand, the one person I know on the hardware side of things at IBM says that the work is interesting, challenging, and fairly busy.