Agree that this should be made into a poll!
For me, Apple Music. My iTunes library goes back to pretty much the introduction of iTunes when I was in college, and I have plenty of MP3s around that started out as pre-iTunes CDs. So, it's awesome being able to have all that live alongside my streaming additions, seamlessly together in one library, cloud-synced to all my devices. Its just very seamless for me and I've never had any issues personally. The day I upgraded to Apple Music, I just went through adding all these songs to my library that I'd been wanting for a while...it was so fun!