Why does one nearby beach work when another does not?

Because they do not face the same water. Orientation, headlands and how deep the tide sits on each bank filter the same swell into different results. Distance along the road is a weak predictor. Valdoviño packs several openings into a short coast: north-facing Frouxeira, northwest Pantín, more sheltered Vilarrube. When one is chaotic, the next bearing is the comparison.