This is a tough call because block and poured have their '+'s and '-'s depending on the variables.
Where I live, the homes have poured foundations because there isn't bedrock for some distance down. So, you can check with what other homes on similiar sites have, and go from there. But the builder is the one who can explain to you why or why not you should go with 1 vs. the other for your site. Of course, if you don't like their explanation, you can ask 'us'. THEN, if you go against his recommendation, it may void any warranty he has. So, tread lightly.
As for moisture and dampness, a lot of that depends on the terrain and the weather. Just because you're on a mountaintop doesn't exclude you from getting water. In fact, I've seen my fair share of underground wells/streams make their 'presence known' at the tops of mountains. Should your builder hit something like this, he may have to alter his plans. You may all of a sudden have a sump pump, or have to 'move' the location of the home, and so on. Again, it would be best to see FOR YOURSELF what other homeowners on this mountaintop have had to do in their basements (or with their foundations) to handle the terrain or underground streams. Ask your builder about a french drain all the way around your foundation, and about putting in a drain and/or sump pump in the basement. All this is cheaper when it's done BEFORE anything is built.
So check your neighbors and do ask questions. I hope others can say more on this. My best to ya and hope this helps.