You'll get lots of opinions from everyone on which truck is best, but the ones you list all have their particular gremlins. I went through a similiar search a couple months ago and was looking for an 05-06 Chevy or pre-03 Ford with the 7.3, or a 05-06 Dodge. I ended up with an 08 Dodge though because the particular truck I found was the best combination of options, condition, and price. So far, so good, but only time will tell.
My advice would be to buy the truck based on the merits of the individual truck, not what other people think about them in general. There are some well known problems with all three that should be considered, but the options/condition/price of the truck in front of you should be the deciding factor.
Good luck with the purchase!