How big does a law firm need to be?

The planned merger of Philadelphia's Wolf Block with a Miami-based law firm to create a giant that would span the East Coast is taking place amid a debate about whether law firms need to be huge simply to survive.

Many firms in Philadelphia and across the nation have adopted an aggressive growth model. But the strategy can pose risks, and there is some evidence that midsize firms can thrive by focusing their practices and targeting regional clients left behind by larger firms seeking a much wider national and even global footprint.

"There has been a huge consolidation in the market in the sense that firms are becoming larger, and the smaller ones are being absorbed by the larger firms," said Milton Regan, a law professor at Georgetown Law Center who focuses on the economics of the legal profession. "It is hard to sort out how much of this is realistic and how much is actually more fanciful."

Regan points out that one of the world's wealthiest firms, New York-based Wachtell, Lipton, Rosen & Katz, comprises only a relative handful of lawyers, about 200, and clearly has rejected full-bore expansion.

Wolf Block, a 317-lawyer firm based in Center City with strong ties to the city's business and political establishment, has been in negotiations for months with Miami-based Akerman Senterfitt, which has 500 lawyers and a large presence in Florida.

The executive committees of both firms have signed off on the deal, and votes by partners at Wolf Block and Akerman are expected shortly.

Leadership at both firms has declined to discuss the proposed merger. But insiders say the firms have concluded that, as big companies pare lists of outside counsel and look to firms that can provide legal services both domestically and abroad, only the largest firms will be able to compete.

Among other objectives, the firms are seeking synergies by combining Akerman's extensive transactional and commercial practices and Wolf Block's well-regarded real estate and estates and trusts departments.

Other firms on a growth trajectory in Philadelphia include the 660-lawyer Drinker Biddle & Reath L.L.P.; Duane Morris L.L.P., 650 lawyers; Ballard Spahr Andrews & Ingersoll L.L.P., with 550; and Pepper Hamilton L.L.P., with 500.

Pepper Hamilton's executive partner, Robert Heideck, said the firm could grow to 1,000 lawyers in a few years.

"When I got out of law school [in 1978], it soon became apparent that the 50-lawyer all-purpose firm could not survive, then it became the 100-lawyer firm, and at this point it is very hard for the 200- to 300-lawyer firm to prosper," Heideck said.

Two Philadelphia firms already are in the very-large category: Dechert L.L.P., with 1,001 lawyers, and Morgan, Lewis & Bockius L.L.P., with 1,455.

Yet not every high-end law firm in Philadelphia is persuaded that the future belongs only to the very largest firms.

Ralph Wellington, chairman of the 200-lawyer Schnader Harrison Segal & Lewis L.L.P., said that the firm would grow over the next few years, but that the pace of the growth was still under discussion.

"I do not share the view that every firm has to [join the ranks of the very largest] because not every company is going to be an international, global corporation," he said.

The 200-lawyer Stradley Ronon Stevens & Young L.L.P. has nearly doubled in size in the last few years, but it also has sought to focus on a few areas, notably financial services, said Jeffrey Lutsky, its managing partner.

"You can't try to be all things to all potential clients," Lutsky said.

Peter Spirgel, managing shareholder of the 70-lawyer Flaster Greenberg firm of Cherry Hill, said smaller firms can offer more competitive rates and are able to focus more on smaller companies. "We see opportunity there," he said.

A recent survey of chief legal officers for 120 large companies by Altman Weil, the Newtown Square-based legal consulting firm, provides fodder for both sides.

It found, for example, that in-house lawyers still were farming out plenty of work to small to medium-size firms.

The survey found that more than half the firms used by those companies ranged in size from fewer than 100 lawyers to 750 lawyers, just below the size of what might be considered a mega firm. Moreover, when the in-house lawyers were asked whether they expected in the future to turn to small to medium-size firms, firms with 100 to 349 lawyers, 78 percent said they would.

Only 2 percent said mega firms eventually would replace their smaller competitors.

Yet the survey also shows that, when measured by the amount spent on legal services, the largest firms are getting a very big piece of the pie. Survey respondents said that nearly 40 percent of the money spent on outside counsel went to firms with more than 750 lawyers.

Firms expanding or preparing to say that in many cases they are simply doing what their clients ask them to do.

Andrew Kassner, managing partner of Drinker Biddle, said the firm made its first West Coast expansion only after concluding that a planned merger in San Francisco would bolster its ability to represent a pharmaceutical-industry client.

In late 2006, the firm pulled off a huge merger with Chicago-based Gardner Carton & Douglas L.L.P., adding 175 lawyers. Each move was based on client needs, not simply on a desire to expand geographically, he said.

"We have been very careful to make sure our growth is strategic," Kassner said.