its not all about the available power, when you are talking about towing differences. Sure both trucks will likely accelerate the same with your trailer. However, the benefits of the Super Duty is with the 'handling' of the trailer weight. The F-250 will shift less due to the influence of the trailer in turns or trailer movement from passing vehicle. Another key difference will likely be the ability to stop. At the end of the day, its not about how fast you can pull a load, but that you can fully control the load and not become a hazard to yourself or others driving around you.
also, the 6.2L is essentially de-tuned from the factory, since the truck was designed to run hard for long periods (a working truck). I can't for sure say the same for the Tundra. That's one of the reasons why the Ford Raptor's 6.2L has more power at the wheels than the Super Duty 6.2L..... Its not expected that the Raptor will be 'run hard, hung up wet' constantly like the Super Duty.