I think the kind of vehicle most desirable depends on the typical task required by each technician. In our company, different vehicles are used for different technicians for different jobs.

Most commonly, we use Dodge minivans and they seem to work pretty well. One of our vans has over 150,000 hard miles on it, and still runs and looks good. We don't label the vans so that we don't alert would-be thieves, though I suppose that it would be very effective advertising for the business. I know that Chrysler has a bad reputation for transmission problems, but I think they are much better after the 1996 models. Brakes don't last very long however-- about twice a year on an average or 20,000 miles.
I think that we load them a little heavy, adding to the brake problem. Ford and Chevy mini-vans seem a little more like trucks with panel sides instead of windows, but I think they drive a bit clumbsy. The Dodges drive just like a car--very comfortable, even after a long day behind the wheel.

For smaller jobs I think the PT Cruiser is great. It's fine for a tech that just runs service calls and only needs to carry 6ft. ladder. If you want to label it, it's great for advertising because it still gets a lot of attention. The techs love to drive it.

For bigger jobs I think the step van or Econoline type van is ideal. It holds up well under all the weight of the tools, wire, and parts. If the shelves don't take up too much room, you can still deliver a 50" big screen. It's ideal for pre-wires or delivering equipment. I do think that it is too big for the smaller jobs.

When I need to deliver something large, such as a large projection TV, I just rent a truck. I have a deal with Enterprise and they will drive it to my door when I need it, usually within an hour. I can get one for about $60.00 per day. Figure it out-- if you only need it once or twice a month, it's cheaper to rent. Otherwise, if you're big enough that you deliver big screens every day, then you can probably justify $40,000, plus insurance, upkeep, etc. for a large truck. Sometimes I think it would even make more sense to just pay a delivery service-- why tie up expensive, hard to find techs with a delivery job, only to have one hurt his back.

One last note. If you use a mini-van or PT Cruiser, get a cage. It's much better for the theft problem, and it adds tremendously to the safety. If you were to get in an accident, a power tool or roll of wire flying at the driver at 80mph could be painful if not deadly.