Does size matter? That's a matter of opinion, and there are no right answers. I can't tell you what to do, but I can tell you what I would do if I were starting over. (There is something to be said for hindsight.)
I've worked for both large and small corporations, and early on in my career jobs were chosen not on objective criteria--career building tenets of training, incentives, etc.--but on a very practical criterion: money. Did the job pay me enough to get by? Very basic, but also very shortsighted. It took me a long time to get to a point where career decisions were based upon actually loving what I do and career fulfillment.
Right now, under favorable conditions, if I were offered a good job with both a large and a small company--and each one offered similar pay and benefits--I'd go with the small company.
Stick with me. In the paragraphs ahead, I'm going to tell you why.
Overall, the umbrella advantage of working for a small company is the thrill of being on the firing line and where the action is. In startup technology companies particularly, that's what gets you up in the morning, raring to go never knowing whether you'll still have a job at the end of the week--or maybe at the end of the day.
You'll be constantly reminded that the battlefield--the marketplace--is just outside. It's the quest for markets, the race to be better than your competition
"It is an important and popular fact that things are not always what they seem. For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much -- the wheel, New York, wars and so on -- whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man -- for precisely the same reasons."