This makes me assume you use an iMp3, well that's catchy too.
By the way I suppose this whole thing should go into http://www.virtuagirl.com/forumTopic.php?foId=9 at the most, if it has any place around here at all, not that I would care.

On the other hand while I'm filling into this form, I could also leave my thoughts on the topic, here:
This question makes no sense on its own. These formats aren't competing, they are for different purposes.
FLAC is for having your audio compressed without any loss in quality because of the compression.
Mp3 is the oldest format that is for reducing the size of the audio file, thus making it better suited for portability, and being compatible with the broadest range of devices.
That is all there is to it. If you're asking this because you want to know if you should choose a certain player for its support of FLAC, then decide whether you are unsatisfied with the quality of your mp3 songs, and if yes and you would like to sacrifice the size of the music collection you can carry with you, then go for FLAC. But even then, you wouldn't always be able to find what you want in the FLAC format.
Finally to make the topic more meaningless: the audible difference between FLAC and an mp3 with better bitrate (192 kbps or more) is minimal or none. On the other hand, nowadays the storage capacity of portable devices and memory cards have increased so much, that FLAC format requires less compromise from the device owner.
So at the end of the day the short answer is: Who cares?...