Gruyere will typically have no holes, and occasionally very small holes. I don't think these are generally ps holes either, as the assosciated taste would be a flaw and make the cheese unmarketable.
Among Swiss Alp cheeses, Emmentaler is an exception. Most go to great lengths to avoid the growth of ps, but the cheesemakers in the Emmental instead developed a process (a difficult one) to encourage it. I suspect this is due to a few factors.
Climate: The natural climate of the Emmental during the summer is conducive to ps growth. It is far warmer in these lower elevations than it will get up in the mountains.
Flora: There would seem to be a strong form of wild ps present in the region. Many varieties of cheeses here have holes, but once you go out of the region the holes vanish almost completely.
My thoughts for a long time have been that Emmentaler must have developed from the Alpkäse of the Berner Oberland. The procedure for making them is almost identical (with the sole difference being that Emmentaler being geared toward ps growth, and Alpkäse geared toward ps prevention, which translates into a higher acidification for the Alpkäse by means of stronger culture development). The strongest evidence for this is that the settlement of the Emmental was very late -like 10th through 12th century AD, and that the primary source of settlement for the southern Emme valley -where the cheese originates- was the Bernese Alps. The culture of the Emmental is very closely linked to the Berner Oberland, much more so than the longer-inhabited Aar valley to the immediate west and north.
Emmentaler also has the exception of being the only traditional 'Alpine' cheese that is not made in the Alps, rather it is made in the lowlands to the north of the Alps (which is why it developed into huge 100 kg wheels). The other Alpine cheeses (Alpkäse, Appenzeller, Gruyere, Sbrinz, Bratchäs, Raclette, and a few hundred more) are all made as part of the transhumance cycle. Emmentaler is no longer connected to this cycle.
So with this, we need to realize that we cannot view Emmentaler as a model or typical example of the Alpine cheeses. A more typical cheese like Gruyere is a totally different animal, developed in a high-altitude mountain climate with the absence of modern conveniences such as refrigeration. The flavor of Gruyere is very very typical of the Swiss alpine family, but Emmentaler is odd and many Swiss actually do not like it. But it has the largest export market by far, in no small part due to the fact that it was the cheese carried by the single most influential group of Swiss emigrants -Amish and Mennonites who were banished from the Emmental and carried this cheese with them to France, Germany, Holland, Russia, and ultimately America. (Guess where decedents of this cheese are made today?)