While I don't know the towing specs for either vehicle I can tell you I pulled my 6,000 lb Safari with a 5.7 liter half ton GM full sized van and a 3/4 ton 6 liter GM van. Interesting was the gas mileage with the half ton van while towing was dead on what I got towing with the 6 liter van. The half ton van had a 3.73 axle with the 3/4 ton van having a 4.10.
The real difference in mileage came when not towing with the half ton van getting about 5 mpg better than the 3/4. I found that the suspensions were quite different with the 3/4 van handling the road dips much better. Overall I felt the 3/4 ton was a step up. Later on it became a wise move since I upgraded from the Safari to a Classic slide out. I never could have done it with the half ton van.
Get those specs on engine, axle ratio and towing capacities. There is a good chance that the Escalade will allow towing in OD, while the Suburban may not. Check the owners manual for further information on that topic. Each vehicle has it's own benefits and if you stay within the 5,000 weight limit, either car will probably be suitable.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700