I had always owned 2x4's and always told my friends "4x4 only tempts you to go places you shouldn't go". My latest truck is a 4x4 because that's the most common for a F250 Crew. Now that I have had a 4x4, it's become invaluable. I have a 37' fifth wheel and several times I had to put a tire in the ditch to back into a tight camping spot. I had to use my 4x4 to get out of the ditch. On several other occasions, I had to back up a gravel camp spot and couldn't get up in 2x4. Hit the 4x4 button, and no problem. We live out in the country on some land, so have to use my 4x4 all the time.
More importantly, if you buy a 3/4 ton truck (which I recommend for many reasons) with the intent of eventually reselling it, a 4x4 will sell much quicker and at a slighter better premium than a 2x4.