We all know these are different. They represent the different culture, diverse employment opportunities, different patterns of behaviors within the team. Which one brings more opportunities? It appears in a big company there should be more. For people who do not like to work hard, it is easier to “hide” when you have the hundreds of peers within your department alone. Hard workers have more chances to build the career.
Then again what is meant by the “opportunities”? In a small company, the path to the top level can be very short. In a year, you are VP, and that’s it. Not mentioning the fact they may not even have this position in the startup. For a change in a corporation, you may spend your entire business life reaching that level. By the time you are there you are DBA, tired and do not have a gleam in your eyes.
Also, I think it is harder to keep the results orientation in a big company. You may not see the forest for the trees. In a startup, you know the results of your activities almost instant. It motivates.
Probably the best would be to try both startup and big corporation experiences in the life. Then you would have more ground to make the choice. Although maybe some people from the small business world just wouldn’t survive in an enterprise and vice versa.