I agree with Jeff's suggestion. Although, just for fun I plugged both URLs into Open Site Explorer and they are really kind of a statistical dead heat, One has one more link than the other, and the one Jeff prefers has marginally better MozRank and Moz trust, but not by much. The overall Page Authority is identical at 13. They probably both could use some love, but yes, it appears you might at the very least have a keyword cannibalization issue. I understand how this happens because it usually results from an attempt to address navigation and try to assure that visitors are finding items they want via several different paths. Frankly, duplicate content happens a lot on eCommerce sites. People often talk about "duplicate content penalties." There is no such thing. It might just cause Google to rank one page and ignore the other, or rank both pages lower because it can't tell which one is really the important one....but it isn't a penalty, per se. Still, lots of duplicate content can cause other problems (like interfere with how much of your site gets crawled on a regular basis), so it's good to address where possible. Canonical tags should do the trick in this case. Cheers,
Dana