I have the '03 Tahoe with the 5.3L and tow package and WDH, towing the trailer in my avatar, at 5900lbs fully loaded. It tows fine. Tow limit on the 'hoe is around 7400lbs, I'm sure the newer ones have a higher weight limit than the '03. You won't win any races towing in the mountains, but it does the job for me in the high Rockies.
If the 'burb with the 8.1 would meet your needs and you can find one at the price point you're looking at, if it were me, I'd sure consider it. You may be disappointed with the Tahoe regardless of the year, in comparison to the 'burb. If I knew then what I know now, I probably would have gone with a Surburban with the bigger engine.
