As someone who recently made the same switch (iPhone to S7):
- Album art never works and the meta data doesn't seem to work as well as it did on my iPhone
- REALLY miss the Siri integration. Technically I can get S Voice or "Ok Google" or even Cortana to work, but Siri worked better for me
- Bluetooth audio works, but iPhone was nice in that the Apple Music app integrated much better. For example, even through BT, I could select artist/album/song/playlists from my MINI without having to mess with my phone. I really REALLY miss being able to get in my car and, without touching my phone, launch a Apple Music curated playlist or radio station from iDrive. No such integration with Android. You can skip tracks and pause, but that's about it.
That being said, text message and email integration is better on Android and Android lets you do a lot more powerful things when you hop in your car and connect to Bluetooth. For example, I can tell my phone to do a certain event or events when it connects via Tasker or similar apps.