You've not mentioned the most important factor, which is not how much weight you'll be towing, it's how far. Short distance, 80 miles or less to and from your campground/ launch a gasser is just fine and dandy. However, if you'll be travelling several hours at a crack on anything other than flat lands, the diesel (whichever brand) will be a fat more enjoyable experience. They're considerably heavier, which makes for more easily controlled braking situations, not relying as heavily on the trailer brakes every time you apply the left peddle). Again, they're considerably heavier, allowing a more stable ride when high winds start to whip your giant brick of a travel trailer. There is so much more to towing than power. Yes, diesels have more torque and a higher resale, but the up front cost is worth it for me, as I travel long distances. At this point, you're the only one here who knows how far you'll be travelling and if the extra upfront cost will be worth it. The current 1500 series are amazing as daily driver's and have the power to move something, but I'd still not select one for ME, as they don't have the weight.
Good luck sir!
