We're half-way through a cross country trip (Buffalo, NY to West Coast), with A 2012 Tundra (5.7) pulling a 8,987 lb. Rockwood 5th (weight certified on "CAT" scale). Running 93 octane this "small block" "gaser" has no problems maintaining 55+ (@ <3,000 RPM) on grades less than 5%. Yes, the rig runs a little slower on steeper grades but ....THOSE GRADES REPRESENT A FRACTION.... of the roads "MOST PEOPLE" travel!
Now, will diesel rigs "pull" better on steep grades, no doubt about that fact but at what cost??? My Tundra rides better than every diesel P/U out there, is assembled by AMERICAN WORKERS in Texas, AND contains more American MADE components than do; Dodge, Ford, or GM. Also, my Tundra costs let to maintain (oil changes for diesels are not cheep) AND cost more than $20,000+++ less any diesel!!! Plus, I get 20+ MPG while not towing and average 10 MPG while pulling. Also, the Tundra's turning radius is less than the other P/U's and it's front end driver's visibility can't be beat.
To be fair, Tundra's 10,000# towing capacity is perfect for just the two of us. If you have a larger rig or have a large family a diesel or GM's 6.0 liter are your only options for 5th towing. I'm not a fan of "turbo" gas engines.... life-time maintenance costs may be questionable... so I'd stay away from that option!
This posting should set off some interesting comments!!!