sync lower quality files to devices when available (FLAC on PC, MP3 on phone)

[Pusher]

Hopefully the title makes what I'd like clear; if not, let me try to explain:

When on a PC with plenty of space, I'd prefer to listen to the higher quality FLAC files of an album rather than MP3's, given the option, however on my phone, where space is pretty limited, I'd much prefer syncing and listening to the MP3 version, given that it takes up much less space.

(forgive me if I use improper terms) What I'd like is an option to tag audio files as being the same song, but a different type of audio file (perhaps if the songs are named the same, with different file endings). When I sync my music to my phone, I'd like to be able to have an option to only sync MP3 files (when the choice is available).

Thanks for listening, and I hope that other people have the same need! I know I'd rather not put a 500 MB FLAC album on my phone that only has 3GB left.

[Spiron]

Good news, MB already has the feature.  In your device sync Settings tab there is a section called "on-the-fly conversion".  Simply click the circle that says "only convert files with a lossless format" to make sure that only your FLAC files are converted to the selected format.  Keep in mind that MB needs an MP3 encoder codec installed if you want mp3, although almost all phones support Ogg Vorbis which both has an encoder provided with MB and is technically superior.
If you already have the files converted however the easiest way would probably to set up a playlist that only has the MP3 files and then to set up your sync so that it only syncs that playlist.  if you have a lot of files, or just don't want to manuall create the playlist, MB does have a rather good auto playlist generator which can sort by audio format through the "Kind" tag.