In general Premiere Pro can read audio in MPEG-2 files. It actually depends on how the audio is written to the MPEG-2 file in the first place.
A mini Dv tape (DV25) has a bitrate of 25, 000 kbps while the average dvd is closer to 5,000 kbps, that means there is up to 5 times as much information available to display your images on a DV tape as in an MPEG-2 file. Mini DV is compressed in much lower ratio than MPEG-2 is, I believe it is either 5:1 or 4:1, I forget though.Additionally, MPEG-2 is not a frame based system where each frame equals one picture, but is a GOP based system. This makes editing it a bit more resource intensive and can lead to your editing application having to recompress the video as you are editing it, which can lead to quality degradation or lag time.
A real question to ask is do you need to that extra quality though. That will depends on how you plan to display your video.
