WordPress performance – send all metaboxes to function or to call it again

Meta retrieval go through Cache API, so retrieving same data for same post during same page load won’t cause database re–querying (and in case of Object Cache even between different page loads).

So that concern aside I would recommend (as usual) to:

  1. Architect in a way that makes sense, not in a way that might or might not be faster (guessing isn’t worth it)
  2. Benchmark the result