Heck, if I got 9 years on the stock battery, and the Sears Platinum is one of those prorated replacements, I would go with the Mopar battery. How much is it worth to you to get another 9 years? Most aftermarket batteries will not last 9 years. It doesn't help if you ever discharge your battery too.
Of course, I was a little strapped for money, so I went with an Interstate Battery. I have never allowed it to discharge and it has lasted me over 5 years. It cost less than $40.00 with the exchange. As everyone will agree, make sure that you clean your terminals until they shine too. This helps to make sure that the battery retains a full charge. Check your ground connection to the engine too. If it is loose, this could mess up your battery.
And, don't get any battery that has been sitting on the shelf for a long time. Even if they tell you it is a brand new battery. I will not buy a battery that has dust and dirt accumulated all over it. If a battery has been sitting on the shelf for two years, you can expect only 3 more years from it. You don't know what the state of the cells are after it has been sitting. But, this is just me. Others may disagree.