Once you convert from lossless (WAV) to lossy (MP3), well, they call it lossy for a reason! MP3 compresses by throwing away some of the information. If you rip at a decent bitrate (I like LAME VBR at the best quality setting), you'll find that the resulting file may sound "just as good" as the WAV, depending on your ears and equipment.
What you don't want to do is rip to lossy and then convert to some other format, because you'll degrade the sound with each conversion.
Ideally you want to rip from WAV to a lossless format (I use FLAC), because the file compresses some, but you haven't thrown anything away, so you could later create an MP3 with the same quality as if converting from the original WAV.
You need lots of disk space, but I always say "disk is cheap". I'm re-ripping all my MP3s as FLAC.