If you want a heavier duty truck for towing I would go with the Dodge 2500 and 6.4 Hemi. If you want/need a lighter duty truck...I think the F 150 turbo V6 could be the answer.
Now I see you're in Toronto...not a mountainous area :). But after our trip a short while ago in the mountainous areas of Montana and Wyoming, I've been rethinking my views on turbo engines.
I live on the prairies, but if I lived in a high mountainous area, I think I would consider a turbo charged engine, to compensate for loss of power that a non artificially aspirated, (non turbo or supercharged) experiences.
I did have initial concerns about the durability of the turbo charger on the Ford 3.5 V6, but to my limited knowledge, this hasn't seemed to be an issue with this engine.
So how does this apply to the OP question. Maybe not a lot, except to say if the OP is thinking of light weight trailers (half ton truck tow rating size) and plans to tow a fair amount in mountainous area....maybe the turbo V6 would be a good consideration.
