Both the half tons are very similar as far as capability. Depending on year I have preferences. Ford with with the 6-spd trans in 2007+, GM in 2009. So if you want a 2007-2008, get the Ford. But GM's 6-spd offers better towing programming IMHO. Ford does not have Select Shift until 2015 which limits the trans from using higher than desired gears or 3rd gear tops, not 4-5. Ford includes 3.73 axle on all Expy EL, GM 3.08 and 3.42 optional for Suburbans and the trans gears are almost the same so 3.73 is "better". The Expy supposedly has higher payload but I have not personally verified that.
I don't know that the huge majority favors the Expy for towing. Owner of properly equipped 6-spd trans GM SUV owners love them.
I don't understand why you say the Suburban has "no tow capacity". The tow ratings for the half tons are inappropriate for RVing, especially with a family on board. The difference is about 8000 pounds to about 9000 pounds with each manufacturer's HD towing package. AT 8000 pounds you will likely exceed both receiver ratings which are about 900 pounds for the Ford and 1000 pounds for the GM.
And GM did offer through 2013 a 3/4 ton Suburban with 9400 pounds tow rating, 2000+ pounds of payload, 6.0L/6-spd/3.73 axle, but that same 1000 pound receiver limit.
GM sells about 4 times as many full sized SUVs and Ford. The Ford offers some great things, but clearly the GM isn't so bad.
If you are looking at a 2015, I really, really, really like the 3.5L Ecoboost!