It really depends on the location of the home. Depending on you want to do with the room and such, that will help determine what to do. In SE PA, crawlspaces are used all the time ESPECIALLY for access. For example, I have heating ducts on the FAR side of our addition. Because of that, we have a crawlspace. Also, we have wiring and plumbing that run through it to the FAR side. If you think of it, you don't want ANY of that 'stuff' in concrete if you can help it. Yes, it's more expensive but for me, it was worth it. Also, if your soil is very wet, a crawl is good to have. It keeps the home OFF of the ground so to speak. And where I live, the crawl is closed off in winter and opened in summer. The soil is wet where I live but just where the addition is. (It happens to be built on a flat portion of the lot. The main part of the house is built on a slight hill by design.)
There are other reasons for one vs. the other. IF you can find out what other homes in your area have under the house, consider that in your 'equation'. And ask the builder why, and why not, as you're already doing. Just be sure you understand the reasoning. If not, ASK for further clarification.