Re: GMC Sierra 1500, RAM 1500 or who is the best?
I've owned a couple trucks (one just outside your years) and pulled the same load with both - my '05 Four Winns.
First up is an '04 GMC Sierra 1500 SLE Ext cab shortbed Z71 4x4 with 5.3L V8 and 3.73 gearing out back. It did OK towing the boat but lost steam going up hills. And it hunted in OD. It was a total abomination of a truck. I had so many things break on it, and weird things at that, that I will not own another one. Here's the short list....Front Axle seal, Rear Axle seal, Pinion Seal, Valve Seals, Transfer case solenoid, fan relay, shifter (couldn't engage Tow/Haul), Cut through the harness running to the driver's door using the emergency brake (routed incorrectly at factory), Radio quit working...I think you get the picture. Absolute pig I will NEVER own one again. Just over 120k miles when I dumped it.
Next, is a '07 Tundra DC shortbox 4x4 5.7L with 4.3 gearing (I think, might be 4.1). It does great towing. Don't get me wrong, on a hill I can tell its back there but I can actually accelerate going uphill with this truck. Almost 99k miles on it right now. Only issue I've had is the waterpump let go. I do my own oil changes so I noticed it was leaking and got it corrected under warranty. Other than that, no muss, no fuss.
Now...my buddy has also offered to use a couple of his Avalanches to tow my same boat a few times. I think his current Av is a '11 or '12 with the 5.3L 6spd and 3.43 (or could be 3.23) gearing out back. Let me tell you...it hunts BIG TIME on hills and flat land. It's a step backwards in my opinion. Ammenities are nice inside the truck (if you've driven a Chevy/GMC pickup you've driven an AV) but the hunting was enough to turn me off on these as well.
His previous Av, probably an '07 or '08 did better with the 5.3L and 3.73 gearing through a 4 spd. Lot less hunting. Still lacked the getup and go needed to actually accelerate uphill pulling my Four Winns.
Go test drive a few and you can make your own conclusions...