only drawback is when full it reduces your cargo capacity by roughly 6lbs/gallon of fuel. so around 250lbs going from 35 to 60lbs.
When we had our 04 duramax, I was really tempted for a bigger tank. Thankfully our 2015 has the 35 gallon tank. enough bigger to satisfy me. I've gone 750 mile non towing without filling or turning on the "low fuel light". Yes 50 or 60 gallons would be nice but not for the extra $$$. Now if the tank was still only 25 Gallons yes. And if I was towing with a gasser, YES.
But it all boils down to what YOU need and desire and are willing to pay for.