Q: Which is actually physically better: MP3 or WAV?
A: They serve totally different purposes. WAV is mathematically perfect, lossless audio. When you record a singer in a million-dollar studio, you save it as a massive WAV file so you don't lose a single molecular drop of quality. But the file size is absolutely gigantic.
MP3 is highly compressed. MP3 throws away audio data it assumes the human ear can't easily hear just to save hard drive space. MP3 is for streaming quickly over a cellular connection; WAV is for professional archiving and mixing.