Wiktionary lists three possible translations for "binoculars":
Google translate prefers binoculares, but also offers prismáticos as an alternative.
Which is the most universally preferred translation?
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My two cents: I favor
prismáticos in Castillian Spanish.
gemelos, although can be used in this context is a word that makes me think of other things, like cufflinks (or twins). Also, I think that
gemelos are a smaller set of binoculars (the ones you would see rich people have at their balconies at the opera house in the movies).
Binoculares is perfectly fine, but would be my second choice after
prismáticos. I don't have a rationale for this, and may change among countries.
To answer your question I used google trends for binoculares and prismáticos and the latter seems to be used almost exclusively in Spain (plus Argentina, Chile and Mexico), so I guess
binoculares is more widely accepted, if we are to listen to Google trends.
I would compare it too with "gemelos", but as you know that is also Spanish for "twins", "cufflinks" and some muscles in your legs (calves), so Google trends would not help here.