What everyone else has said plus, do you have a special concern? For me I must drive into the northeastern states, read that NJ or divorce the DW. So the 250 can use the left lanes, some parkways, park on the street, while the 350 cannot. Most cops don't care, a few do.
I maxed my 5er to an 250 size truck, it is a "half ton towable". That is as big as I will go, as long as the pick up must occasionally make the trip to NJ with the pickup.