I have had both a gasser and now a Duramax. I personally like the diesel towing experience better. Is it worth the extra expense? To me it was but that's just me. I do love the sound!

I also have become a big fan of the exhaust breaking feature.
We get 10-12 MPG when towing. Always better MPG when we go through our 1st tank of non-California diesel.
When pulling with the gas truck it was always 8-10 MPG.
I agree with a prevoius poster that my truck really drinks DEF fluid when towing in the mountains. Just came back from a 8 day trip to Utah and I got a low def warning about 60 miles from home. I filled it up before we left and we traveled about 1,700 miles. I imagine some of this is due to the higher MPH we are allowed to tow at in other states. I always carry an extra cube of DEF so no big deal.
We keep our vehicles for 15-20 years so the extra 10 grand for the diesel was not a big deal to me.
You know it really comes down to buying what you want and what makes you happy.
The research has always been my favorite part of buying a new vehicle.
Fave fun and safe travels!