Pretty sure you will generally get a bigger tank with 3/4 or 1 ton. My F250 has a bigger tank than my F150 did. Lots of variance by year and model.
I regret not buying a SRW F350. No size difference from F250 and both or rough daily drivers as a Super Duty but the extra payload is nice. If you decide diesel, definitely go with one ton because the heavier diesel will negate much of your payload gains with the 3/4 ton.
I'm not a fan of towing with half tons but they really have gained capabilities in recent years, at least regarding a 7500 lb TT so they might be a model out there that suits your needs.