Twenty five years ago I was diving the Monterey California area and had a VW superbeetle. I remember hauling all my gear plus six tanks in that thing. Not the ideal scuba mobile, but it did the job.
I've never had the luxury of having a vehicle just for scuba. However, for my business I bought a 3/4 ton GMC Cargo van. The bins you could get for free merely get in the way. I like having the space. When I use it for diving, I put a chair in it and change inside. Changing in a heated van after an ice dive is the only way to fly.
I also ride a road bike and use my van to transport my bike to club rides. Thats a road bike as in Lance Armstrong, not Wille G by the way.
Pure versitility, comfortable,A/C for summer, Kick ass heat in winter, real live ground clearence and one heck of a payload capacity. You can't haul ten students(only one really cute one), but you can haul all thier gear and still have room for a 150 qt drink cooler. Who could ask for anything more.
Jim