Warren Buffett

FORTUNE — The activist investors in Omaha this weekend for Warren Buffett’s annual Berkshire Hathaway brk.a meeting don’t necessarily own shares in the company or even subscribe to the Oracle’s investment philosophy. That didn’t stop them, however, from debating the way Buffett and other high-profile investors exert their heavyweight influence to reform companies — including Berkshire holdings Heinz and Coca-Cola KO .

At a cocktail hour following a dinner hosted by Columbia University and GAMCO Investors’ founder Mario Gabelli, which featured Pershing Square’s Bill Ackman, the consensus view was that company management matters little when activist shareholders are in charge — even at Berkshire itself, as well as many other businesses.

Buffett’s approach to corporate governance has been criticized lately after the Oracle declined to vote against a controversial compensation package for Coke executives that he characterized as “excessive.” But investors found Berkshire’s recent purchase of ketchup maker Heinz more illustrative of Buffett’s evolution. In the Heinz deal, Berkshire partnered with 3G Capital, which is known for its aggressive cost cutting and management reform at companies it acquires.

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Buffett doesn’t usually do that kind of overhaul, which often involves replacing CEOs and making other tough decisions, with Berkshire acquisitions. But Buffett’s partnership with 3G surprised investors like hedge fund manager Whitney Tilson, who noted that Heinz grew its Ebitda (earnings before interest, taxes, depreciation, and amortization) by 50% in the year after the acquisition — growth generally unheard of for a mature business, Tilson said. And he thinks Buffett won’t stop there: “I think that Warren Buffett and 3G will team up again to buy Coke,” he said. “Anything that shakes up corporate boards is a good thing, because there are a lot of companies that are just fat and poorly run. Take Heinz.”

Buffett, for his part, defended his abstention on the Coke vote as the annual shareholders meeting opened Saturday, saying Berkshire got the result it wanted anyway (Coke is reconsidering its compensation plan, according to reports from the Wall Street Journal.) “That was the most effective way of behaving for Berkshire. We made a very clear statement about the excessiveness of the plan, and at the same time, we in no way went to war with Coca-Cola,” Buffett said. “I don’t think going to war is a very good idea in most situations, and I think if you’re going to join forces in going to war with somebody, you have to be very sure about what that alliance might mean.”

A debate over another controversial alliance surfaced in Omaha Friday morning when Tilson was hanging out with Ackman and they saw that Gabelli had criticized Ackman’s activist tactics on CNBC. Ackman, who is known for his campaigns against Herbalife hlf and J.C. Penney jcp , recently teamed up with pharmaceutical company Valeant vrx to attempt an acquisition of Botox-maker Allergan agn , of which Ackman now owns nearly 10% — a move that Gabelli called unfair. Ackman and Gabelli declined to offer comment.

Tilson, who himself rails against “dreck” companies that make up his short-selling book, said that he thought Ackman’s Valeant maneuver would benefit all shareholders by delivering a deal that otherwise would not be possible, as Allergan has repeatedly refused Valeant’s offers. “I hope more activists put more companies in play in my portfolio,” Tilson said.

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Renowned mutual fund manager Wally Weitz, whose investment in Valeant has recently replaced Berkshire Hathaway as his portfolio’s largest holding, was more conflicted. He winced discussing Ackman’s approach to buying Allergan. “It’s not technically illegal but … there’s letter and there’s spirit.”

On the spectrum of how useful shareholder activism can be, “Ackman falls somewhere in the middle of that,” Weitz said. Ackman’s “quick hit” move in buying Allergan stock to make it harder for the company to block a takeover makes him slightly uncomfortable, Weitz added, and he worries that the activist pressure could take a toll on Valeant, perhaps inciting bad management decisions. “I’m not sure it will be a long-term holding for us,” he said.

Still, Weitz also thought that Berkshire Hathaway might grow more active in reforming the companies it invests in going forward, particularly after the successful partnership with 3G on Heinz. Reflecting on that deal, he recalled Buffett’s remark that “there are 100 companies that could use a 3G.” Added Weitz, “I love Warren. The way I like to describe him is, he’s flexible.”