Hi Kevin, car or aircraft models can often be pretty sophisticated shapes with a lot of variation and subtle changes throughout the shape, as you certainly know.
It tends to be a difficult type of model to work with just in general, no matter which mechanism or software you choose to do it in...
But several things can depend on the specific goals and desired output. That's why I was asking for some actual images or samples of what the original poster was interested in doing.
If you're trying to do a highly detailed "reverse engineering" type job where you're going to be constantly making a lot of small adjustments to localized areas of the shape, that kind of a thing does tend to fit much more in the "organic sculpting" type workflow which suits subd modeling a lot better. Of course that doesn't mean that it is automatically an easy thing to do it in sub-d, a beginner should still be prepared to spend quite a long time refining the particular skill set to make that work well.
Another interesting aspect is that actual manufactured cars themselves are designed using a combination of physical clay models and NURBS software. But designing something to be manufactured tends to be a significantly different process than modeling with a focus on rendered appearance only instead.
I would certainly agree that MoI tends to be more suited for doing concept style work rather than detailed replica modeling.
There are actually several examples of different vehicles that have been done with MoI in the Gallery on the web site, some links:
