Sometimes the distinctions that contract drafters are most vehement about are those that happen to be spurious. Consider, for example, the pointless debate over whether to use between or among in the introductory clause. (See MSCD ¶ 2.21.) It’s similarly unnecessary to make a fetish of using stockholder rather than shareholder—in contracts and elsewhere—when the corporation in question was formed under Delaware law.
Insisting on this distinction would seem odd, in that stockholder and shareholder are synonyms meaning—no surprise—a holder of shares of stock in a corporation. The distinction would seem to derive from urban legend rather than legal scholarship—the only reference to it that I could find online was a vague reference in a recent law review article to how stockholder “is the preferred statutory term in Delaware.”
Presumably no one is under any illusion that which term you use in a contract could affect a party’s rights. More likely, the distinction derives from wanting to show good manners by conforming to local custom. But in this case, local custom would seem to be far from clear cut. I was reminded of this topic by a post by Gordon Smith on Conglomerate Blog, and he does a good job of describing how both terms are used in the Delaware General Corporation Law and in Delaware case law. To that I would add that the standard treatises on Delaware corporate law use the terms interchangeably.
So there’s no question—for all purposes, including contract drafting, you may with a clear conscience use either stockholder or shareholder when referring to owners of shares of stock of a Delaware corporation.