To this question, the only thing we can answer you that is 100% true is that the best ham in the world comes from Spain, both the raw material and its preparation, and that the best and most appreciated pig, as far as the exquisiteness of its product is concerned, is the acorn-fed Iberian pig.
Having said this, we know that the best hams in the world are bred and produced in Spain and that these are Iberian hams fed on a montanera diet.
With these characteristics, there are 4 areas in Spain in which these conditions exist, as a forest of cork oaks, holm oaks, gall oaks or oaks is required. These trees are the ones that give as fruit the acorn

What 4 areas produce these exquisite pigs?
Salamanca:
The reference town with a D.O. in its power is Guijuelo. This ham is characterized by softer and more balanced flavors. Its lower temperatures during the curing phase mean that it dries less aggressively and consequently has a generally less intense flavour. Practically all palates like it.
Extremadura:
This is the area with the largest area of pastures. An excellent ham, with a higher degree of intensity. An excellent choice.
Huelva:
Jabugo is the reference village of Huelva in terms of ham.
Like Guijuelo, it has its own D.O. In general, it is the one with the most intense flavours, due to the more aggressive drying process due to its temperatures and to the type of greater cutting of fat, characteristic of the area.
Córdoba:
The reference place for the ham from Córdoba is El Valle de los Pedroches. It has a D.O. and it is one of the 4 areas that is least known to the consumer. However, its ham is of excellent quality and its name is becoming better known. Its hams are usually quite intense and tasty.
In addition to these well-known areas, there are others in which this type of ham is reared and produced, such as Seville, Cadiz…
Again, this question depends more on the consumer’s personal tastes than on any other measurable variable. Any ham from these areas and that quality, will live up to your expectations, so take the opportunity to try them all!