Costom tunes are much better & safer than a tuner. One size fits all doesn't apply here. I've had tunes for 50K towing the mtns in Az heat and it gets better mpg and have had no issues @ all. A good tuner + a good valve body will enhance it without harming it. Most tuners do not have enough control of the trans stratagies. Mind you you will need to tell the tuner what you want the truck to do and if towing heavy be conservative. My tunes extend the redline of the eng, different conv lockup timing & shift points are speed controlled not throttle position.
My particular chip can be shifted on the fly. On the flats I run in my 20 Tow tune, when hitting more grade I just lift and switch to my 40 tune and go on up the hill. The eng will make power more efficiently
Look @ my sig. Everything was done to enhance my towing experience. Been happy so far.
Now this is just my preference and decision. Do some research on the tuners sites, call & talk to them. They will be glad to explain the difference better than I.
When I first started I ran a Hypertech programmer. My custom tunes are quieter & my 40tow tune makes more power than pos 3 on the Hypertech that was supposedly a 100hp setting.