There's a lot of choice for playing your music on Android. For every option that plays music from your local storage, there's one that pulls music from the cloud and streams it. Both have their advantages, as well as disadvantages. Streaming can play havoc on your battery and your data allotment, but the almost limitless catalog of tunes is pretty handy. Conversely, it takes less juice and no data connection to play from your device itself, but you're working with limited space.
Personally, I do both. I keep four or five of my favorite albums on my phone, and I use Google Music to stream the rest of my collection. What about you? Let us know in the poll!