We rented from Hertz for our stay at CKS. I got the SUV because small car with people plus luggage does not work out so well. Of course you only need this to and from the airport but I also prefer the comfort. A nice SUV will also be the bigger car on the road in a place like Thailand. I have found driving in a country like this bigger is better. When renting the vehicle and doing the walk around with the rental agent take pictures of every part of the vehicle and make sure they see you doing this. This will keep them from trying to charge you for any damage no matter how small when returning. Of course this will not apply to any damage you might do but this will also protect you from the valets at CKS.
We had two villa's for our stay, 4 adults 1 child and I am a Diamond. Not really a big difference in perks from Diamond to Gold at CKS. They did give us free breakfast for all 4, I guess we got this since I had both villa's in my name.