If you want to go to the West of the USA (Washington, Oregon, California, Nevada, Arizona, New Mexico, Colorado, Utah, etc) as a tourist, you may have to decide whether to rent a car or a motorhome. As this decision is setting the course to how you are going to spend your holiday, here's some pros and cons for both car or motorhome/recreational vehicle(RV). Please keep in mind that this entry is written from the view of a European tourist who has to fly to the USA. So some of the things described may sound trivial to US citizens.
Driving the Vehicle
Almost all rental vehicles in the USA have automatic transmissions. If you have driven automatic cars before, there should be no problem for you. If you haven't, it's really easy. Just be aware of your left foot; it may try to hit the clutch (there isn't one) and instead you'll perform an emergency brake. You'll usually do this for the first time even before you leave the rental company's yard.
Most of the streets are really big, straight and wide (compared to most European roads), so the size of the vehicle doesn't really matter. Driving a 27ft RV is just as easy as driving a van or a compact car. Just keep in mind that the vehicle is longer and wider, but there's enough space. Some RV rental companies have limitations on what roads you are allowed to use. You may have to stay on paved roads, and all damage to your RV caused by gravel roads will not be covered by any insurance. The same, however, can be said about most car rentals. If you have some metropolitan areas on your schedule, you may prefer a smaller vehicle. It's easier to park and to drive within the cities. Here's what a German tourist said about driving a 27ft RV over more that 3000 miles within three weeks:
I had absolutely no problems getting familiar with the RV. It had a really powerful engine which made the vehicle very agile. Even when there were signs saying 'slower traffic keep right' we were never 'slower traffic'. I had driven vans before, and it was not my first time with automatic transmissions. The only situations when I wished to have a smaller car was when we wanted to drive into the cities for dinner, especially when our campsite was some miles away (too far to walk, that is). Getting the motorhome out of the campsite space, driving into the town, finding a parking lot for dinner and getting the RV back into that campsite space at night time would have been much easier if we had had a smaller car. It was not really a problem, just a loss of comfort.
When you rent an RV, you have your accommodation with you. You don't have to search for a place to eat, to rest, to drink, to change your clothes, to sleep1. If you don't want to spend your holiday penned up in a relatively small car, don't trust the descriptions of the RV rentals. If the description reads 'RV sleeps four adults and two children', this usually means that you can pack these six people into the RV by using every spare inch to squeeze everyone in. You'll also have to sacrifice one of the greatest advantages of the RV - the easy sleep without much preparation. You'll enjoy your holiday far more if you rent at least one size bigger. The aforementioned RV, designed for six people, is a good and comfortable choice for two adults and up to two kids.
If you rent a car, you have to search for a place to sleep every night. You have to unpack the car for the night and to pack it again in the morning. You can't cook your own food and you have to store your clothes in the trunk. You can't sleep in your car. On the other hand, it's much easier to find a hotel or motel if you have only a car to park (instead of an RV), and even when travelling with an RV, you may want to sleep in a real kingsize bed from time to time. You might think that staying somewhere for the night is easier in the RV, as you don't have to find a motel, you don't have to check in/out, you don't have to get your luggage into/out of the motel. This is not absolutely true. Your RV needs some care everyday: checking the fresh water, grey water and sewer tanks2, connecting gas and electricity, dumping the sewage from time to time. Most of the campsites offer the 'full hookup'. This means that you can connect your motorhome to fresh water, gas, electricity, sewer, cable TV, and so on and so forth.
Cooking, Eating and Drinking
If you're travelling with a car, you don't have any work, you just have to order and to pay when you stop at a diner, inn, or restaurant. You can do that with your motorhome as well, naturally, but that's not how an RV travel is supposed to be. With the RV, you can drive to a supermarket, buy food, drinks, everything you need to prepare a tasty meal, and cook whatever, whenever and wherever you like. RV are usually equipped with a fully functional kitchen with oven, stove, microwave and refrigerator. When you return from a half-day's hike, you will appreciate the opportunity to prepare some fresh coffee or tea, or a warm meal.
Nothing beats the feeling of sitting (with your seat belt locked, that's the law) in a comfortable chair at a table, reading a book or eating a sandwich while your partner is on the 'helm' of the RV. You usually have a refrigerator and there's no need to fuzz around with a cooling bag. You have an oven to prepare coffee on and you have your own restroom. This may be one of the most important advantages of an RV over a car; when you take over the RV, you also take over your own restroom. You can be sure that it has been cleaned thoroughly, but you may want to do that yourself again. From that moment on, it's only up to you how clean it's going to be. No one else is going to use it. This does not mean that you are going to encounter dirty restrooms in the USA, you just may feel safer if you know that no one else has used it before you.
You might think that travelling with an RV is less expensive than driving with a car and paying for every night at the motels. This may be true if you stay at expensive hotels, but not if you use motels. First of all, the car costs much less to rent than the RV. During the holiday high seasons, prices for RVs are really high, whereas rental cars are generally less expensive and the rent does not rise that much in the holiday season. RVs consume significantly more fuel (car: 10-12 l/100km or 20mpg compared to motorhome: 23-25 l/100km or 10mpg). However, costs are not really a criteria to decide between motorhome and car. The costs are similar for motorhome rental/campsite fees/self-made food on one side and car rental/motel fees/eating on the other, with the motorhome being slightly more expensive. As all these prices are subject to change, you'll have to check that for yourself.
This is a highly individual matter. There are people who do not want to take care of a motorhome when on holiday and prefer the comfort of hotels, motels and easy driving. Others would never want to leave a national park for the night if there's a campsite within the park itself. This is one of the greatest advantages of an RV; many national parks have campsites within their grounds. They may not offer a full hookup, and usually they are operated on a first-come-first-serve basis. But if you have ever experienced a night in, for example, Sequoia National Park, sitting under the trees around a campfire (that's allowed there), and having your motorhome (with a filled fridge!) behind you, you may never wish to travel with a 'standard' car again.