Our clay soils do heav and fall as with the climate and our scampy rain falls.
It is my educated opinion based on reading and talking with people in the business that both are not any good with our proper watering in, but with watering in, and maintance, a slab is better.
A slab, if watered in and water maintained, has more square footage on the ground and disperses the homes weight more evenly. A peir and beam has all the weight on 15 to ??? piers.
Set out a soaker hose, the black weeping one, and use tent stakes to stake it about 16 inches all around the home and water that foundation during our brutal summers once a week. When the dirt pushes away from the foundation and leaves those 3 foot deep crevices, the damage already happening. Keep that soil evenly, balanced, moist.