Don't just look at the wheelbase. The ratio of the rear over hang to the wheelbase of the Tahoe is the same as the ratio of the rear over hang to the wheelbase of the Suburban. This creates similar dynamics and the two vehicles will tow similarly. Our Envoy XL was far more stable towing than our Suburban was. This was due to the shorter overhang of the Envoy XL (wheelbases were within 1" of each other).
I was pleased with how our 5.3L/4speed/3.42 Suburban towed our 5000GVWR HTT. It did tow our current trailer fine, but there is a major ride and handling improvement when going to a 3/4 or 1 ton vehicle when towing 7500#.