Is it lithium ion? Or the older one? If it is the older one I would think about getting the lithium one and if you look around a lot of places will take your older one on trade for $25 credit. But I do like having all of my batteries fitting any tool, so that kind of a toss up. My decision would come down to size, if you like the smaller compact impact you wont be dissapointed with the new DeWalt 12V from what I have heard around here, otherwise maybe go with the 18. Personally for $64 dollars I dont see the need to buy a new battery. When I wear out batteries I have either updated to a newer battery style like when li-ion came out, or I buy a new tool with the same batteries as they usually come with 2, the tool and the charger for the price of 2 batteries.