Disclaimer--I sold vehicles/RVs very successfully for many years in the PAST!
But so many of you on this forum are acting like the "stereotypical" salesman...NOT listening to what the guy said!!!
The post title says GAS, he has said he understands the difference and does not want a DIESEL..
His question was about difference from F250 to F350.
To the OP, check insurance differences as someone mentioned but also licensing regulations.
If you order or buy an F250 with the larger tire option and a camper pkg or other pkg, you can get your payload to essentially the same as a F350. Howevwer the payload rating on the truck will remain lower and in some areas this can have a huge impact on licensing costs.
In Ontario at our store we order our F250 with a downgraded GVWR sticker that lets you avaoid annual safety and emmissions tests plus buy lower tags ratings. The truck itself is not downgraded as far as capacity. Saves money every year going forward and the truck is as capable as a basic F350 SRW.
And a 6.2 gasser will tow the fiver anywhere you want to take it, albeit a bit slower on some mountain grades but it will get you there just fine.