Foundations - Slab or Cross-beam?

I'm not a home inspector or a real estate expert by any stretch. That's why when I read home descriptions and it says "Foundation: Slab" or "Foundation: Cross Beam", I don't really know the difference. To me, if a house has a foundation it must be a good thing. This past weekend, I actually learned that there was a difference - a big difference according to my agent. A slab foundation is actually considered inferior to a cross beam foundation because it is usually done for cheaper constructed homes. What's the difference you may ask?

This is what I learned:

Slab foundation - a cement foundation is laid directly onto the land - compressed and graded soil. It is essentially like it sounds, a big slab of cement that sits on the bottom of the house. It is solid and usually has many of the pipes encased within the cement as well. It works great if the ground doesn't shift (if it does, you'll start seeing buckling in the floor) or if your pipes don't need work (if they do, you'll have to dig up the cement to find the right spot to repair the pipes). Allegedly, slab foundations are done on cheaper homes - tract homes, etc...

Cross beam foundation - unlike a slab foundation, this type of foundation has crawl space. It is raised above the soil and the majority of the house does not sit directly on the land. Thus if water leaks down a hill or the ground shifts, it won't affect the house too much. The base of the foundation sits on the dirt while the actual house is slightly raised. This is supposedly the preferred type of foundation.

This all makes sense to me, but what is everyone else's experience with these type of construction? Any contractors, experienced realtors, or handymen - your opinions and thoughts would be great appreciated. Does a home with a slab foundation command less money? Is it less desirable? Does it only matter if the house is built on a hill? If I didn't hear it from my realtor, I would never even know the difference.

Any experiences, anecdotes, or otherwise anyone would like to share?