There's only 1 reason to use WAV (Playback), it would be its already decoded for you. WAV is perfect for CPU's that cannot handle FLAC, but that's about. I remember seeing threads talking about how FLAC Level 4 to 5 is good enough but I crank it to Level 8 and all my equipment can decode it just fine.
Here's an example of a modern device that has decoding limitations.
Here's an example of a modern device that has decoding limitations.