personal preference is chevy/gmc. looks, ride, power, reliability. with either gas or diesel they make good tow rigs.
for gas motors a big block from any of the big 3 works great. lots of torque, reliable motors, just not the best on fuel. best (stock) fuel economy i'm aware of is the gm 8.1L at 13-15mpg, offered in the 2000+ era though was discontinued a few years ago when fuel prices spiked. my 84 k30 with a 454 gets 9-12 depending on how i drive and what i'm towing.
small block gassers pull well, though on long steep inclines you will lose speed. most get better fuel economy than the big blocks, but not always.
diesels. all 3 of the newer diesels will pull great and each has their issues. with the 90's era motors the more powerful options were the ford 7.3L and the 5.9L cummins. gm had the 6.5L, was not designed to be a powerful motor for a 3/4 or 1 ton tow rig. easiest on fuel and capable of towing medium loads (single car or truck on a trailer) in stock form was definetly the weakest option. there are upgrades available for it and about 600ft/lbs of torque can be reliably reached. the 7.3L and cummins can both handle significantly more than that.
dodge finally got their auto tranny situation up to a reasonable setup in 06, though gm has had the most reliable auto of the 3 since the 80's and that still hasnt changed. th400 (3 speed 80's), 4L80E (4 speed 90's, not its 1/2 ton brother the 4L60E), and the 5 and 6 speed allison. manual tranny, all are very solid. gm discontinued theirs about 2 years ago, ford is following suit with the new body style so dodge will be the only option (stock) for those that desire a stick shift in a new truck. dodge had an issue with the nut that holds 5th gear in place with their 5 speed in the 90's but there are upgrades to fix that.
