@Tad,
I'm glad you asked about the weight difference, and if the Jet Sled is worth the extra weight.
I ordered a Jet Sled Jr from Cabela's, added 10 grommets and a single 3/4" aluminum angle runner with 3 bolts/nuts/washers, and it weighs 5 lb 12.6 oz. Then I ordered 2 more of the same sled from the same place, and they both weigh 6 lb 5.6 oz without modifications. I'd assume the first sled I got is not typical.
For comparison, the modified Paris Expedition weighs 5 lb 1.2 oz with 6 grommets and 2 runners of 1/2" angle, with 6 bolts total.
The Jet Sled Jr is 21 inches wide at the top, and 17 inches wide at the bottom. The Paris Expedition is 20 inches wide on top and only 13 inches on the bottom. The extra 4 inches of width makes the Jet Sled less likely to roll, and the deeper single runner resists sliding more effectively.
I don't notice any extra drag from the runners on either sled. The main problem is icing in warm conditions, which happens to skis and snowshoes too. A single, shorter runner means less scraping. You can't put a single runner on the Paris because there's already a center molded plastic runner.
The plastic on the Paris sled is thinner and more flexible. The center Jet Sled runner has more weight on it because the bottom is more rigid. The single runner in the center tips the sled slightly. I think that will allow the edge of the metal runner to dig into ice and resist side slipping even more, like an ice skate or metal ski edge.
One unexpected advantage of the single, deeper, and shorter center runner is that the Jet Sled Jr will turn on a dime, without going forward. The dual runners on the Paris sled kept that from happening, and the sled would tip over if you tried to turn too tightly.
The front of the Paris stays at a 45 degree angle all the way from the top of the sled to just 1" above the bottom. The Jet Sled Jr starts curving 3" above the bottom. Theoretically, the Jet Sled Jr should go through soft snow easier than the Paris. I haven't tested the Jet Sled in soft snow, but I do know that the Paris gets very hard to pull.
The Paris Expedition is 18 inches longer than the Jet Sled Jr on the top, but so much of the length (and width) of the Paris sled is overhanging plastic lip that you really only get 6 or 8 inches more usable length in the Paris. What's more, the lip of the Paris is angled downward, which means it scoops snow into the sled.
So in summary, YES, I think the Jet Sled is well worth the extra weight. One big advantage is that it's available for purchase, and the Paris Expedition isn't.
The best deal on the Jet Sled Jr at the moment is from http://www.sportsauthority.com (Search for Jet Sled). They're selling it for $29.99 with $2.99 shipping.