If those are the only options, then the coordinating conjunction must be but. Coordinating conjunctions are words that connect two clauses, phrases, or words by treating them equally - one is not dependent upon the other. If those two are clauses, they must be independent clauses that together form a compound sentence. Besides "but", coordinating conjunctions are "and" and "or".
Humans are better suited for making art than making war
Explanation:
The author compares the beauty of what man can create - 'musics that matches the birds', 'laugher that matches the dogs', 'understanding more intricate than a spiders web' and contrasts it to the horrors of war 'breaking open breasts', etc.
