I recently blogged about what I look for when considering where to work: http://henrikwarne.com/2013/03/26/what-do-programmers-want/
The three main criteria are "the product is software", "great colleagues" and "challenging problems". Small/large is not on the list, but maybe I should have added "having a high impact".
The biggest difference for me is the impact ypou have. In a small company, your own contribution is a much larger part of the total output, and that is very satisfying. Frequently it also means faster turn-around time - what you do gets deployed much quicker.