[Porsche-O-Phile]

Generally speaking conditioned crawl spaces are considered to be higher quality construction. However (as has been said) you will pay a penalty in cost - both up-front and in recurring (it costs money to condition it).

Another alternative that nobody has mentioned is having access panels or lined trenches with cover plates. Ugly as sin, yes but if you have some sort of raised floor above it with a nice finish, you'll never see it and it could potentially save you a lot of $$$.

Another nice thing about lined trenches is that they can be sloped like the piping so if there's a leak it goes away from the building, not creating a septic tank underneath it - as someone has mentioned is a potential problem with conditioned crawl spaces...