Agree with flying farm. Depends on which trailer has the amenities that you want. Is the wear of each trailer, tires, LQ condition, and overall conditon of the horse compartment the same? Just becuase the 2003 is newer, that doesn't mean that it will last longer. Use and how well a trailer is taken care of should make your decision.

BTW - how many horses do you plan on hauling? If you are going to purchase the two horse, does it have a hay rack? Might want to think about how you travel with your horse(s). We have a 2 horse LQ and place hay on a hay rack for a week or longer ride - it works for us, but some folks prefer the three horse to store camping stuff/hay if the first compartment with a stud wall. So I'd make a pro and con list between the 2 or 3 horse based on how you plan to use it.