They are probably much of a muchness. I would recommend taking out the additional accident insurance with a British company before you depart as the policies they hard sell you to cover you over and above their basic insurance are very expensive.

I have traveled through the west coast of America 2 years ago and we had organized road trip that included a visit to main and key destinations of the west coast. We came to Las Vegas by plane, where we rented a car after 2 days of sightseeing and visiting casinos. We had a small problem with the rental because we didn´t book in time, which is why my advice is certainly to book a car on time, a week before your arrival, sou you can get the best car at affordable price. The car was great, and after a period of 10 days of driving and traveling around the coast, the cost of everything has turned out cheap and reasonable per person. Some friends of mine have done the whole journey traveling by plane, which is stupid for me because like that you miss a lot of destination on the way.