as a newbie 3 years ago I felt most comfortable buying a full ton (3500) Ram. Even with the weight of a diesel, 4x4, and megacab, I have 3900 pounds of payload. I just didn’t want to end up with ‘too little truck’ and after spending several years researching I still wasn’t exactly confident in my calculations or abilities. Our TT is under 10k pounds loaded so it’s not even an issue for us, but I like knowing I never have to worry about it. As you said the 2500/3500 really aren’t bigger than the 1500 these days.
Everyone doesn’t need a 3500, but if you’re planning on towing more than a tiny teardrop, popup, or similar, I don’t like the idea of 1500/150 for regular, long distance towing. Having a safety margin built in is nice.