However, not all brokers in New York are required to co-broke with all other brokers. Specifically, many MLS member firms will not co-broke with those not MLS members. Since more brokers and agents are REBNY members than are MLS members, doesn't it make sense to go with the organization with the greatest reach.
Also look at the quality of that Internet presentation. Is the firm's web site well-designed and easy to navigate? How about the quality of the photos and floor plans (if any)? I've seen some pretty pathetic web sites out there from non-REBNY-member firms - they are a turn-off to direct buyers as well as to potential co-brokers.