I still don't understand people's love for the .MP3 format. Lossy compression might have been necessary 15 years ago when data speeds were slow and storage was still expensive. There's no reason for it nowadays. Unless the music is poorly-produced, a CD will always sound better than .MP3. A high-rez .FLAC download is, of course, another story, but most people have no way to play those without a computer. You're always better off getting the .FLAC download if you have a choice, though, because it's easy enough to use software to transcode it to another format while keeping the original .FLAC. Put differently, there might be some reason why you want or need a lossy-compressed file at the moment, but if you download the .MP3, you're stuck with it in the future because most places won't let you re-download in a different format at no cost when you want a higher-quality file later. If you download the .FLAC, that's not an issue.
I still find it mildly amusing and mildly pathetic how many people incorrectly refer to devices like the iPod as ".MP3 players." Part of what made the iPod a good device for its time was that it didn't force any single standard upon the user.
(With all that said, an .MP3 is better than nothing when it comes to things like a concert bootleg.)