Sarasvathy likes to compare expert entrepreneurs to Iron Chefs: at their best when presented with an assortment of motley ingredients and challenged to whip up whatever dish expediency and imagination suggest. Corporate leaders, by contrast, decide they are going to make Swedish meatballs. They then proceed to shop, measure, mix, and cook Swedish meatballs in the most efficient, cost-effective manner possible.
In other words, corporate executives plan, while entrepreneurs improvise.
Actually, there is no way to excerpt the article and do it justice. Read the whole thing. I should point out, though, that it simply replicates previous work: the research in Amar Bhide's The Origin and Evolution of New Businesses, a book that deserved to be much more widely read; and my own Under the Radar, a book that may have been more justifiably ignored.