The two villages are only 6 kilometers apart, but there are fundamental differences between the two.
So which is the one for you? Well, it all depends on what will make you happy, so if you want a larger village then it has to be Olvera, with a population of 8,500 is is more than four times the size of Pruna. This means four times more bars, restaurants, and Brits, so if you a very social animal then Olvera will suit you better, if you want a quieter life then Pruna is for you.
Pruna is so small that you quickly get to know the inhabitants, but the foreign population (Icelandic, American, Belgium, Dutch, Russian, English, Chinese, and Welsh) are less than 3% of the population. This smaller group of ex pats can mean that the pool of similarly minded people is reduced, not quite enough people to arrange for clubs and classes, enough that you will groups of Brits in the bars.
In Pruna still see donkeys used to carry things, people ride horses through the village regularly. It is a working Andalucian village and really authentic.
Olvera is a major tourist attraction, being one of the Pueblo Blanco's, in fact being the queen of the Pueblo Blanco's. Being so large it has escaped the devastation that has happend to the other Blancos, which are full of tourist tat, Olvera has kept it's personality, it just gets a bit crowded on the street occasionally. And parking is hell. The streets can be staggeringly steep.
Out of the holiday times I can walk out around Pruna most days and not bump into another ex pat during the daytime, I like that. But if you want more choice of daytime company the Olvera has the bigger ex-pat community simply because it four times larger. Evenings you can find groups of expats in both villages
Olvera has a more arty ex-pat population, and Pruna has a more retired population plus a couple of photographers and tech types. The 'gad abouting' techies I know like it because there are no distractions, and there you have it, a small authentic village with no distractions. However at the moment I know of two artists and performers moving into Pruna, so perhaps pruna will soon have it's own artists colony (in order to be witty here I looked up the collective noun for artists, and it is . . . . . colony . . . . , oh the bitterness)
Health wise both Olvera and Pruna have a 24 hour health centre, I have only used the Pruna one and it is excellent.
Public transport wise Olvera has many more buses going to Malaga, Ronda, and Cadiz, Pruna has two buses a day to Seville and to Olvera. But the Pruneans just get lifts to Olvera, the 6 kilometers is no real problem. (I hitchhike there)
Both Olvera and Pruna have very low priced properties, the benefit of being 90 minutes away from every major airport means that it is on the fringes of easy travel. But you get much more bang for your buck in Pruna, much bigger houses with more outside space for the same or lower price. This also means that the population of Olvera tend to be wealthier and continue to travel even after buying in Olvera.
The Pruna swimming pool is much nicer than the Olvera one, but the Olvera one has a nicer restaurant by the pool. The Pruna market on a Friday is much bigger than the Saturday Olvera market, which only sells clothes.
Pruna has many more squares than Olvera, something I hadn't noticed but was pointed out to me by a newcomer, it means you can always find somewhere beautiful to sit all over the village, which can be hard in Olvera.
Olvera has a Mercadona and several small DIA's as well as the local supermarkets, Pruna has several small local supermarkets and a Coviron. They both have similar DIY shops etc.
With the exception of one street (which I, of course, live on) Pruna is much flatter than Olvera. This is of concern to some people who dislike vertical climbs to their homes.
And I don't know if this makes any difference to anyone, but Olvera is in Cadiz county, and Pruna is in Seville county.