I did a trip from LAX to PHX trhoug Vegas and Grad Canyon in a Dodge Challenger.

I can't think of a better car for the job. It has very roomy interior, leather seats, satellite radio, and is very fun to drive, not to mention it looks stunning. It also has huge trunk for its class.

Down side is fuel economy. That thing is thirsty, but hey, it gives you the 5.7L hemi to play with.

As for SUV's your best bet is reserve a full size SUV and ask for upgrade, tell them you could opt for something smaller as long as it's nice and comfortable.

worst case you will get something like a Traverse or Arcadia (thats what I got), which are fairly well equipped. or if you are lucky you may get An Infiniti FX or QX or even a Benz ML or something. Make sure you turn down the Escalade because it will probably won't make the distance between 2 gas stations in the desert.