I used Google for a while, It's a great product but the user interface sucks. I will stick with Spotify, since they removed the offline songs limits have increased my respect in the company. By the way, either in Spotify or in Google Play Music you will not listen the songs in Hi-Fidelity in free plans, just in Premium ones... And with a good earphones, listening in HiFi is really another level of experience.
Even in the past the limit was 3.333 songs per device among 3 devices (9.999 offline songs in total). Now, this limit was raised to 10K songs per device, among 5 different devices. 50K offline songs in total. This is a HUGE upgrade!