I've used 'Switch' for quite a while now, and I like it. It will convert into a wide variety of MP3 bit rates, including variable rates. It has worked flawlwssly for me.

My stuff on Soundclick is in the default and locked [ for the free accounts ] rate of 128 kbps, which is less than my preferred rate of 192 kbps. Variable rates are best for quality vs size, but many players cannot play the variabale rate MP3's.

The more complex harmonically the music is, the higher bit rate is needed to capture the nuiances of the recording. At about 320 kbps, even audiofiles have been unable to tell a difference between a CD and an MP3. Those that maintain that they can virtually always fail a blind A/B test. CD's are at 1411 kbps, so there is considerable compression, even at 320 kbps.

There is, as Mac has suggested, a variance in quality among MP3 converters, so you might try a few before you decide on a default one.

Fire, the wheel, and the I IV V -- foundations of civilization.