First, I haven't seen ogg files in a long time, I never use them so I don't know what's up with them. wav files are technically higher quality than mp3 because they're uncompressed, but mp3s take up so much less space. I have a music file I created which in its wav form is 40MB, but converted to mp3 is 3MB.
For this reason, I suggest using mp3s because the difference in quality (as far as I know) is not noticeable, but the difference in size is definitely noticeable.
Hope this helps