I not 100% certain, but i think the 2014 2500 is the only one that comes with the new rear coil suspension, I think the 3500 still has the leaf springs. This might be a big factor as far as ride comfort goes. I really like this new set up in my 2500. I don't think you would max out the payload or towing in the 2500, but again, not sure what all you might be doing in it
Yes the 2500 has the rear coils and the 3500's have leaf.
To the OP, for what you are towing get the diesel. here are a few pluses and minuses going with the diesel.
minus;
1) Initial cost is more
2) oil changes is more expensive… but you can go 15,000 miles between oil changes on 13+ cummins powered trucks so its actually equal to the gas.
3) Don't like to idle a lot.
4) they don't like snow plows due to the added weight of the engine, not saying you can't put one on it but you are limited to size and weight of the plow
Pluses;
1) you get your money back on resale.
2) will last longer
3) better overall milage.
4) you can tow more and you don't have to worry about over working it as you will kill the truck before the engine.
5) manual transmission optional
These are just a few of the + and - of owning a cummins. I'm sure there are more but thats all i could think of at the moment.