It's been discussed to death, so you can search and probably find a few more threads about it.
But, in a nutshell... Renting an RV will cost roughly $2500. Pros: You have a real home, with A/C, a hot shower, a real kitchen with a real fridge, a nice bed, etc. as well as total isolation from dust storms. And, when you roll into Black Rock city after a long time on the road, you immediately have shelter.
Cons: You have to get all your stuff out of it and clean the entire thing immediately after Burning Man, when you really just wanna go home and "decompress" for a while. And it costa lotta.
A tent is a LOT less expensive. Pros: More opportunity to decorate and be "artsy" with your shelter, less commercial looking, and you're one of the "hard-core" burners who is more connected with the playa. Some people say tenting is a more social way to go.
Cons: It's hot as hell and dustier than hell. You're out there on the desert floor and you can't escape it. When you roll into Black Rock City after a long time on the road, you are faced with immediately having to erect and set up your camp so you can rest and kick back.
Comfort level is up to you. You can bring camp showers, kitchen/cooking facilities, and sleeping arrangements to suit yourself.
There is Option Three: for the same money or less than renting an RV, you could buy an older model camper or trailer.
Too much is not enough, and when in doubt double it.