MP3 or WAV — pick by what happens next
MP3 is compressed and small, plays on everything, and is the right answer for listening, sharing and archiving speech. WAV is uncompressed: perceptually identical to the source track, roughly ten times bigger, and the right answer when the audio is going into another editor, a transcription pipeline, or any process that will re-encode it again. Encoding to MP3 now and re-encoding later stacks two lots of lossy compression, which is audible on music and on quiet speech.