my last Suburban

The new Tow Ratings Guide list nothing higher than 8,500 for Chevrolet Suburban/Tahoe/Yukon. Perhaps the 2500 series is no longer available.

Comparing a 1/2 Ton suburban to a 3/4 Ton truck is apples to oranges.
Having owned 2 1/2 Ton 1500 series suburbans, it is a night to day difference with the 3/4 -2500 series Suburban which I have now. For starters, the 2500 has leaf sprung rear suspension, my suburban barely squats when the trailer is hooked up, before I tension the weight bars. The 1/2 Ton would squat severely. The engine seems to work less, but that could be from the 6 speed heavy duty transmission, higher rear end ratio, or the 6.0 engine. It is all around more truck. The rear axle is a full float heavy duty axle 8 lug.
I wish Chevy would make the 3/4 Ton available to the general public again. As I understand, it is only available through the fleet purchase program.

Dick, no one is happy with the Surburban only coming on a 1500 chassis but GM doesn’t believe it can make money with a 2500 version. Isn’t that why Ford stopped selling the Excursion?

Interestingly enough, I tossed the new Tow Ratings Guide as I'm not in the market. But............is the Suburban you mentioned a 3/4 ton? If not, that would answer all your questions. 13000 sounds like the new standard for a 3/4 ton and 8300 sound very 1/2 ton-ish

1. Bigger engine built for heavy duty use.
2. Less vehicle (crew cab truck vs suburban).
3. The Suburban is on a 1500 series chassis, with small drive train parts like axles, transmission and so on (relative to the 2500HD truck).
4. More cooling ability with the 2500HD which has enough grill area to cool a turbo diesel that can tow more than 23,000#.
5. Different suspension under the truck vs the suburban. Suburban suspension is built for a smooth ride with the ability to tow. The 2500HD is built for towing and hauling and having a comfortable ride is less of a priority so they engineer it accordingly.
6. The 13,000# tow rating likely means 4.10 axle ratio, the suburban likely has 3.42?
7. And so on.