The music is the only really good part of the prequels, so I voted Duel of the Fates. Don't much care for the overly choreographed lightsaber duels though.
When rewatching the series early this year, I told myself to pick out at least one positive thing for each prequel movie besides the music. For Phantom Menace I chose the Naboo starfighters. They just look cool, and I believe they were still practical effects back then which I've always considered better than CGI.