I've had to work out of both over the years, and I can tell you a van is far far better. Put a bunch of tools and materials in the back of a pickup and leave it somewhere. Now try to feel comfortable about leaving thousands of dollars worth of stuff just sitting there where any yahoo can come along and swipe it.
Or, when it's raining out...... you really gonna feel good about all your tools turning to rust?
OK, you say, I'll get a service body or a topper. Well, didn't you just convert the PU into a van?