By Stephen M. Silverman
Updated September 15, 2003 10:00 AM

Most of this week’s water-cooler talk revolves around the breakup of Jennifer Lopez and Ben Affleck, but Variety has focused its eye on another split involving the leading man — the one with his onetime “Good Will Hunting” Oscar-winning co-writer, Matt Damon.

By the trade paper’s calculation, the fellows haven’t written anything — either alone or together — in six years, despite their Academy Award for Best Screenplay.

And, although they co-produced HBO’s “Project Greenlight” reality series (thus reinforcing their image as professional partners), they have embarked upon two distinctly different acting paths.

Affleck, 31, has made 20 movies (starting with the blockbuster “Armageddon”), while Damon, 32, has made 17 (kicking off with the title role in the more serious “The Talented Mr. Ripley”).

At the moment, says Variety, Damon’s in Europe, filming “The Brothers Grimm” and preparing for “The Bourne Supremacy” and, early next year, “Ocean’s Twelve.”

Affleck, meanwhile, is mostly in the tabloids, though he did a memorable turn a couple of weeks ago on the “Tonight Show,” when he read the awful reviews of his flop with Lopez, “Gigli,” to host Jay Leno.

He also just finished director John Woo’s “Paycheck.”

Analyzing Damon’s professional output, “Ripley” producer Bill Horberg tells Variety: “Matt’s someone who’s been very smart and careful about he does. He’s not just looking to go to work and pick up a check.”

As for how the two actors compare, an agent opines: “Arguably, Ben Affleck is a bigger movie star than Matt Damon. But Matt works very hard at surrounding himself with talented directors and challenging material. Ben has become more of a personality.”