Pick up truck:
- Flexibility, can carry many bikes of different shapes and
- Easy to clean after carrying dirty bikes
- Bikes are partially protected against collisions.
- No need for costly accessories (but you
can add them if you want)
- It is extremely unlikely that you reach the weight capacity limit of the car with bikes alone.
- Pick-ups are longer than most SUVs and station wagons
- Don't have an enclosed trunk and if you need one, you may need to install an accessory to overcome that.
I drive a mid-size pickup truck and it is the most flexible option I've experimented. Besides the pickup, I have used roof racks on a station wagon, rear mounted racks on a SUV, and hitch mounted racks. All of them have size, shape and weight limitations that can be easily overcome with a pickup truck for most cases. Even some tandem, recumbent, trikes and quads can be carried with a truck with no special accessories.
You can use accessories but you can also transport one bike with no accessories at all.
The single most basic accessory of all is a cargo bed liner, which is general purpose and protect both the car and the load. I add Cargo straps to secure the bikes against movement and a cable lock to secure them against theft. From there on, you can get all sorts of fancy mounts, tail gate pads, etc.
When I drive alone to a trail, I simply "toss" the bike in the cargo area and go. But when I go with friends I can easily accommodate 4 bikes. With some care, even 6 bikes using no more than a couple of ratchet straps. If you add roof rack and hitch mounted rack you can carry way more bikes than riders fit inside the cab (...).
Another great advantage is that the bikes come dirty after the ride, It just does not matter, I can hose-wash the bed liner or use a broom to take the dirt out.
Another thing that I like is that the bike is reasonably protected from read end collisions and they are not high up so they are not as prone to hit low structures like a garage door or a low bridge, a drive-thru roof, etc.
One disadvantage of a pickup truck may be the open cargo area is prone to theft of lose items when parked or even at a trafic light stop. I have installed a cargo cover that can be rolled up to solve that issue, so it is like having a very large trunk. Perfect for luggage and other stuff. It also serves a purpose when taking the bike to/from the service shop, as I can leave the bike in the car while being protected from sun/rain and it is out of view of thieves and curious people. A camper or truck cap can also solve this issue, even though it can limit the shape and or size of the cargo you can carry.
Finally, I am a DIY enthusiast, so carrying small quantities of materials (especially sheet goods) every now an then is another use case that fits perfectly for me. It would take a lot to convince me to use another car type.