It's a tough call. I used to have an 04 2500 with the Hemi and a 5 speed, and it delivered more low end torque then my current truck, which IMO does not pull the trailer as well with the tune (91 octane), as it does without.
The tune appears to be more of a performance tune for racing then for towing. I've tried all the tunes and still feel that I get better towing performance and mileage with the factory tune. I have also noticed there is a difference between the 1500 and 2500 factory tunes. The 2500 is definitely tuned for more low end torque.
It's just my opinion, but I don't think you will find much if any benefit under the operating conditions you indicated, but I could be out to lunch. Hopefully there is someone that has actually used a tuner on a 2500 in a HD towing application can offer real world data and experience.