The Chicago Board Options Exchange and International Securities Exchange agree on this much: Narrower price increments, and the tighter spreads that might come with them, hurt liquidity for some market users.

Executives from the two exchanges contend that the Securities and Exchange Commission is making a mistake by expanding a pilot program, which started in January 2007, to include even more options.

Other exchanges aren't so sure. NYSE Arca has apparently benefited from the program. That exchange's market share for non-index equity options increased by three percentage points in the first two months of 2010.