What's the TPI of the older tires? If they're also 120TPI and a pound heavier that's insane. If they're the 90 or 60 TPI version that's a lot more understandable.
JJ's are great tires. They're best in the other three seasons - they slip on loose snow, when tires like Bud & Lou or Johnny 5's keep gripping. Great that they'll basically work for your conditions all year.