Some economists have looked specifically at this question...
In the paper "Small business and job creation: dissecting the myth and reassessing the facts" (from Small Business Economics in 1996, link: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=420303 but full paper behind a paywall)
Their conclusions (from only the U.S. manufacturing sector between 1972 and 1988) were that:
Large firms dominate both job creation and destruction
Gross job creation and destruction are higher for smaller firms
Net job creation rates don't show a strong relationship to firm size
So it sounds like, at least for manufacturing, gross job creation may be higher for small firms, but gross job destruction is also higher, meaning that net, there's not an advantage for small businesses.