Assuming it's a general Yosemite visit...see the sights, take some hikes, bike around, have a picnic, etc., I'd guess that staying outside would be more enjoyable. Mariposa and Oakhurst both are 1-1.5 hours from being parked in the valley, or you can head up to Tioga Road, Glacier Point, etc. In the more crowded areas, you just have to park a normal sized car instead of a small bus. Also, the Wawona area and Mariposa grove are fairly close to Oakhurst. With the long days of summer, you can get in early if you want, and stay until you feel like heading for dinner, a shower, or a swim at the hotel. Prices and choices for food are better outside of Yosemite. Or you can maneuver around a too-big RV through crowded traffic to find a parking spot where you can all pack in to the crowded RV to cook dinner and sleep.
I suppose if you plan to cook your meals, the RV would be an option, but the Yosemite West rentals or similar places may also be an option and you're not stuck in an RV in a smoky campground, or in line hoping to get a spot in that smoky campground. Whether there are adults and kids, how many, how long the visit will be, all might affect your choice, but even considering the extra driving, in summer I'd think a place outside the park, and driving a normal-sized vehicle would just overall be easier and more pleasant.
Gary
Yosemite Photo Galleries: http://www.pbase.com/roberthouse/yo