I'm going to say go with the cheaper of the thicker ones. You'll have slightly more cooling capacity, and since your going with a smaller radiator that won't be a bad thing. I don't think 1 lb of aluminum is going to matter much. Also, I'd try to get one with plastic end tanks for weight, not an all aluminum design. Below is a comparison of a two stock Tercel radiators. From back to front: 93 manual, 88 automatic, 1990s civic radiator. I did a weight comparison between the three and the savings from the largest to the Civic radiator was only like 4 lbs with water in it.
