The 2500 vs 1500 is a matter of strength for me. Just about everything is heavier duty. The 2500 is rated to carry more payload, and will tow more, which for me is not a big deal, my camp trailer is less then 1500LBS and the boat is less than 4500LBS but because the truck is rated for more it has a beefier frame, bigger axles, stronger steering, bigger brakes, and in the case of Dodge it gets you a straight front axle instead of IFS (this is a huge debate over what is better, but it is my preference)
as for reliability, this is my second Dodge, I had a 2004 that I bought new and sold with 185k miles. Never did a tune up, never had a break down or an issue, just changed oil and air cleaners it ran like a champ. I bought the Power Wagon with 72k miles on it, and have just over 150k now and the only issue has been the electronic sway bar got stuck, but seems to have worked its way back free. I am definetly a Dodge guy, but I think with any of the full size trucks on the market now days you get a pretty solid platform.