A 2500 series rides completely different than a 1500 does. If you aren't towing or hauling regularly, the ride in a 2500 can be quite unpleasant. Cost difference also. Ride height is much higher making it more difficult for people to get in and out of, larger wheels/tires, etc.
A 1500 is more than most need, and if you can get 30 mpgs on the highway for a small premium (let's face it 2.4k over a 3.5 ecoboost is almost not noticeable considering the MSRPs of modern pickups) I fail to see the downside. It'll be slower, but tow about the same, ride about the same, cost about the same, but you get a significant MPG increase. Oh and the resale is going to be better. Go price out diesel vehicles vs their gas counterparts. This is a pro for buying them new, and a con when buying used.
This is honestly the only downside I see: the 3.0-liter Power Stroke diesel will be offered in the 2018 Lariat, King Ranch, and Platinum trims. They leave out the XL and XLT trims amazingly...