But balance has a figurative element as well. A truly balanced wine will have tension and energy, as with German rieslings that walk a tightrope between cloying sweetness and mouth-parching acidity, thrilling as they teeter back and forth, or great Champagnes that crackle with a vivacity that demands another sip.

The flavors of a wine must also be in balance, as with the push-pull between bitter and sweet so typical of many Italian reds. This, in particular, was where we found too many of the Bierzo wines in our tasting falling short. We loved the aromatic fruitiness of these wines, but quite a few showed an off-putting bitter quality that was out of proportion to the other elements.

What may have caused such a disjointedness? I can only speculate, but I would guess that either the grapes were not properly ripe at harvest, or the wine was overworked in the cellar, as producers tried to manipulate or eke out of the wine more intensity than it had to offer.

“It really depends on where mencía grows,” Gil said. “It’s got to have balance, but it’s hard to handle properly, like pinot noir.”

Though we were perhaps more aware of the misses, our tasting had its hits as well, like our No. 1 wine, the 2010 Vico from Raúl Pérez. Mr. Pérez is one of the superstar winemakers in northwestern Spain, and his wines always show great purity and definition. This wine was burlier than his more graceful Ribeira Sacra wines, an excellent example of mencía made in a slightly warmer climate, with fruit flavors buttressed by mineral and oak accents. Yes, it was beautifully balanced, and it will reward a few more years of aging. At $35, this was one of Mr. Pérez’s more modestly priced wines. Other cuvées can soar past $90 or $100.

Our No. 2 wine, the 2011 El Pájaro Rojo from Losada, was a juicy, fruity, structured wine with spicy, herbal notes unburdened by flavors of oak, unpretentious and pleasurable. At $16, it was our best value. We also liked a slightly more expensive 2009 Losada, which was earthy, smoky and still a bit tannic. It was our No. 5 bottle.