One of the benefits of a larger range tank is you can be more choosey with where you purchase your fuel from.
i.e. You can hold off that little longer until you reach a town where the price is so and so, and fill up there.

Having a larger tank can actually be quite benefitial financially, without even realising it.

BTW. You don't say whether you have a short or a long bed - I assume you have a long bed because you tow a 5'er. Is that correct?