I realize I'm quoting a bit older post here but this was exactly my experience. The 3V V10 is horrendous when towing (I had 5R110 and 4.10s). The go-slow pedal is basically binary: off or on. Because it's so gutless there's near zero modulation within the travel of the pedal -- if you're into the throttle 20% you might as well be into it 90% because there's no discernible difference.
In contrast my 6.2/6R140/4.30 is WAY WAY better, but it's still no diesel or even close. However on the same grades in the Rockies (which is home for me) with the same loads it pulls harder, has far better throttle response and modulation, and gets better mileage.
Around town I'll lock out the top two or three gears so it's not lugging 6th at 35mph
Regardless, with all these new gassers you need to adjust your brain to spinning the motor fast and for extended periods if towing. They don't even begin to wake up until 3k rpm and that's just the start.