Yeah, Google Play Music is pretty great. I've got a few iPhone users on it. The iOS app is well done. The ability to cloud upload up to 50000 tracks (and you can do that even with the free version if you don't want to pay a monthly fee for new music) and the added bonus of Youtube Red at no extra cost (no ads on youtube) makes it a sweet deal.
It's pretty simple to move to Android. If your contacts are linked to a mail account (gmail, exchange,etc) then it's a no brainer. If they're on iCloud you can log into the icloud.com website, export them all to a vcard, and then import into a gmail account (which if you don't have, you'll need for Android apps). It's easy.
iOS and Android all do the same stuff anyway. All the griping and moaning, of which I am guilty too, is pretty much about user preference. At the end of the day, they both work fine and are pretty similar.