Do the 'Burb, although any of them will be fine.
I'm assuming the Tahoe/Suburban's you are looking at are C or K 1500s. Those use the 4L60E transmissions. They are not bad but are prone to damage due to over heating. Fluid should be changed every 50k miles, so if you find one with service records, all the better. In either case, change the fluid immediately and use Dex VI, not the Dex III that they came stock with. Dex VI is a synthetic blend and runs much cooler than Dex III, and is backward compatible with the older 4L60Es.
It would not hurt to add an axillary transmission cooler. Stacked plate type is best, but any extra cooling is better than just stock.
