Can you hear the difference?

I tried ripping a cd using foobar2000 to FLAC and to Vorbis (medium compression). I could hear the difference easily in the HF detail. In fact, Vorbis medium and Vorbis low compression (high quality) were differentiable also. Vorbis high quality was hard to tell from FLAC, but the file size was getting pretty big too.

Not to say it's critical. My favorite stream comes through on MP3 192, and it sounds very good, though the fact that it's always a modern quality recording (within a year or so I think) probably helps too.

The lower the bitrate the easier it is to tell the difference, that is no surprise. The question is if there is any point on the spectrum where lossy files cannot be distinguished from losslessly compressed files like FLAC. The BBC have done some research, and their conclusion is that at 320kbs few people if any can tell the difference. Of course, to test this, the method has to be double blind, and involve a sufficient number of repeats and participants to be statistically significant. However, all the serious reserach (rather than anecdotal) seems to confirm this. On the other hand, this will become increasingly irrelevant when bandwidth is getting cheaper and cheaper. The BBC itself is currently streaming experimental broadcasts of losslessly compressed 16/44 FLAC files.

@timlub 

What makes WAV sound better than FLAC? Is it the fact that decoding FLAC impedes the flow of audio electrons from the computer?

Both WAV and FLAC are lossless formats. The better one is FLAC because it not only has lossless quality but also small size. Regarding to the Spotify music, it you want to download the best quality, I'd highly recommend you convert spotify music to flac format. DRmare Spotify to Flac Converter should help you. You will still keep the ID 3 tag info, MetaData, year, album cover, artist and so on. 

As far as I known, one of the most lossless audio format is FLAC.  FLAC is short for Free Lossless Audio Codec, one of the most popular lossless audio formats for lossless compression of digital audio.
As for Spotify songs, you can listen to high-quality 320kbps audios offline. But for free users, you can only play lower audios online. 
In order to avoid this hassle, you can use AudFree Spotify Playlist Downloader for Windows to convert Spotify to FLAC with one click no matter you are using a free or paying account.