Designed by Daniel P. Coffey & Associates Ltd., the proposed Horner/HAS structure would include 250 to 275 condos and have a bull-nosed shape reminiscent of the historic Flatiron Building in New York. The new building would sit on large columns above the Hahn Building, a landmark building in the center of the block, creating an open space between the roof of the Hahn Building and the new tower.

That part of the design was intended to preserve the image of the landmark building, rather than make it appear as if the facade was merely grafted onto the base of the new structure, says Daniel Coffey, president of the Chicago-based architecture firm.

A two-story restaurant shaped like a flying saucer would overlook Fountain Square, a drab public space that the developers would renovate at a cost of $2 million. The restaurant structure would feature a rooftop plaza that would be connected to the square by a curving grand staircase.

“Our goal was to make the ground-floor area come to life,’” Mr. Coffey says.

The block is “arguably the best block in Evanston,” says John Mangel III, vice-president of development and acquisitions for HSA. With a movie theater and El and Metra stops nearby, downtown Evanston has “a lot of the amenities that the city of Chicago has to offer in a smaller setting with proximity to the lake.”

Messrs. Klutznick and Anderson agree, though they contend the block isn’t big enough for two big projects.

“The question is whether the block should handle that kind of density,” says Mr. Anderson, president of Northfield-based Focus Development Co. “We just don’t think that’s the right thing to do.”

City Manager Julia Carroll did not return a phone call for comment, though Mr. Mangel says city officials have “reacted favorably to our proposal.”

Messrs. Klutznick and Anderson contend their plan is superior because their tower would sit on the north end of the block, farther away from two neighboring high-rises, and it doesn’t tinker with the landmark Hahn Building like the competing plan does. Yet the 523-foot tower they have proposed is likely to draw opposition because it would shatter the height record for suburban buildings.

Reflecting growing concern about the impact of the development boom in Evanston, the City Council was scheduled to consider a 180-day moratorium Tuesday night on new downtown construction. Developers of both projects say they submitted their zoning documents early enough to avoid the moratorium, though they likely wouldn’t begin construction this year even without it.

Chicago-based HSA, a full-service real estate firm, would be responsible for developing the 30,000 square feet of retail space in the new project, while Mr. Horner, who has developed residential projects in Evanston and Chicago, would oversee the condos.