When I bought my Disco, I also got my dog, a GSD. I advocate the crate because there are times where the crate is better then the LR guard. In an auto accident, its another layer of protection. If you have to take along a ton of gear, and fold the seats, then you have your dog on top of your gear or they'll figure out a way though the gap between the guard and where the backrests should be.
I used to do search and rescue with my dogs, and there were times when I had to leave my pup back at base for one reason or another. It was required to have a crate, so that if it got hot we could put them outside in the shade, and not the the car. There's just not enough ventilation back there.
As personal experience, a dog is extremely destructive. My GSD destroyed the cargo bins in the back, the rear door bin, scratched enough to break the rear defroster plug and a few of the horizontal defroster lines in the glass. In the end, I wish I would have gotten a crate in the first place.
The disadvantage is that it may take up space, and you'll have to put the rear seats up each time - which is a pain. I put mine on the driver's slide, since it can obscure my line of sight on the passenger side, and increase my blind spot.
If you do a bit more research, you'll find that dogs actually like crates. Too many people use it as a punishment, but if you use it in a positive manner, they'll naturally go to it. Its like their own room/den. My dog was crate trained when I got her, and it sits next to my bed - when I go to bed, she goes to her crate. I never close the door.