In one corner, a scrappy New Yorker with a savvy southerner at his side. In the other, a heavily favored European powerhouse first stunned by the fury of a rival attack, now starting to punch back.

Nasdaq OMX and IntercontinentalExchange of Atlanta are battling Deutsche Börse for NYSE Euronext, the product of a 2007 merger that owns the world's most-recognised stock market and a profitable European derivatives arm.