One big difference I have noticed is how much more work seems to matter at a small company. When I've worked for a small company it has always been that the company sells X or desperately needs X, so they hire me to write X.
At larger companies the goals have been more abstract. Work might be to satisfy an ideal created by management ("testing is good! 30% more testing!") which may or may not actually be useful. In the worst case it's entirely possible to do work that nobody actually cares about, which I find demoralizing. I don't think that happens as much at small companies because I don't think they can afford it. Big companies with old cash cow products and lots of inertia can.
At larger companies the goals have been more abstract. Work might be to satisfy an ideal created by management ("testing is good! 30% more testing!") which may or may not actually be useful. In the worst case it's entirely possible to do work that nobody actually cares about, which I find demoralizing. I don't think that happens as much at small companies because I don't think they can afford it. Big companies with old cash cow products and lots of inertia can.