I would suspect the heavier battery would have the most capacity. Battery plate surface area is a big part of what determines AH ratings. Larger plates would have to weigh more.
Also, go for the most recent manufacture date. I couple of yrs ago I was at Wal Mart and watched a customer return a battery. It was the top of the line wal mart batt. A knowlegeable employee used a device that measures the battery's internal resistance to check its condition. It gives a relative value of "cranking amps" and sure enough, the returned battery was not up to snuff.
He checked the new one, no good at meeting its spec. Another new top of the line battery also didn't measure up. As I watched I ask if he would check the cheap $29 battery. Several of them all measured up to spec. They also had more recent manufacture dates. I concluded the more expensive ones stay on the shelf longer, cheaper ones turn quickly. Who knows...

I'd go find a fresh "Interstate". They have always performed well.