This depends on where the house is & what kind of soil it is on but overall I like post-tension foundations best. They crack a lost less & are more stable.

The traditional stem wall with a wood framed floor is the best. These are also the most expensive. It is easier to live on a raised wood floor and there is less chance of problems with radon gas and moisture.

Post tension slabs are often used in production houses because they use less concrete and therefore it is less expensive especially when doing a number of houses at once and it doesn't crack easily with expansive soil.

However, you can use a thicker concrete slab and a stronger concrete mix and not use post tension. Post tension is difficult to remodel later on. You can't cut into the slab without being very careful not to cut a post tension wire.

Do you have a soils report? The soils engineer will usually give you some alternative options. Your contractor can help you with pricing each option and you can make a decision from that information