NOT all South African wine styles are equal, and what determines relative strengths and weaknesses may have less to do with climate and location (loosely speaking, the key components of terroir) and more to do with wine-makers, and the examples set for them.

For example, one of the best performing Cape wine categories is the so-called white Bordeaux blend, a combination of Sauvignon Blanc and Semillon - of which a portion is usually barrel-matured. It is not a particularly prolific class, and even in the biggest competitions never attracts more than 30 entries. However, it yields a disproportionate number of medals. If you had to make an arbitrary choice from a wine list you are more likely to get a bottle worth drinking from white Bordeaux blends than any other category.

The red Bordeaux blend class does not deliver the same set of odds, nor does Sauvignon Blanc, Chenin Blanc, Pinotage or Shiraz. Since there are many fine wines made from them and some have very visible and well-managed associations driving their objectives and publicising the achievements of the top producers, there is clearly an anomaly here.

It is easier to explain the success of the white Bordeaux blend category than it is to account for the other classes making such comparatively slow progress.

Semillon-Sauvignon Blanc blends are relative newcomers to the South African wine industry, with no noteworthy examples produced before the turn of the century. As a category, it rose to prominence on the back of a single, high-profile and consistently successful example in the form of Vergelegen's white estate wine, now marketed as Vergelegen GVB.

As a result, Vergelegen defined the game, and has also established the pricing centre of gravity. Any producer seriously contemplating a berth in the same squad knows the entry criteria are high, but that the rewards justify the effort. In short, the class came to be determined by the consistently top player as much as by the limited availability of Semillon. There has been no real dilution since then.

The same cannot be said, for example, about red Bordeaux blends, even though the category began life in much the same way. Meerlust was one of the first exponents and Rubicon was fashionable from the outset. It remains one of South Africa's most successful super-premium brands.

Nevertheless, the category has been undermined by its relatively low entry criteria. Anyone who can source Cabernet and Merlot can be in the game. While Merlot was something of a rarity in the early 1980s, it was embraced with more enthusiasm than competence as soon as planting material became commercially available. In little time there was a lot of unexceptional wine around, driving down price and devaluing image.

This also explains why the efforts of the producers' associations - Chenin, Pinotage, and Sauvignon Blanc - have not yielded dramatic results. Those who join and campaign for better wines and more rewarding price points are in the minority. Grape growers far outnumber actual producers. This means there are vast quantities of bulk available for anyone who wants to participate in the same category.

Take Chenin, for example: probably no more than 5% of the vineyards are truly old and ideally located for premium wine production. These are the fruit sources used by wine-makers producing the exceptional wines promoted by the association. The remaining 95% simply serves to undermine the image and compromise what the vanguard is trying to achieve.

Strangely, this is not all bad news for wine drinkers: the less homogeneous a class, the better the opportunities for bargain hunting. Poor performers dilute the brand equity of the whole category. Astute buying is more likely to yield undervalued treasure among red Bordeaux blends, Pinotage and Chenin than among the supremely confident and very coherent group of Semillon-Sauvignon Blanc producers.