If you have recorded all of your audio using a sound card or recording device capable of recording 24-bit audio, you will want to master your material at that bit rate. This will preserve the headroom and allow you to have the levels up to 3 db below clipping and still have a strong sound. When working in other bit rates, you will have to come up much closer to zero db, just below clipping to get the same dynamic range as 24-bit mastering.
The bit rate that you use to record, mix and master audio will have an effect on its sound. Lower bit rates often sound as though they have some audio missing. The 24-bit audio sounds better than 16-bit audio as long as you are listening to it with quality speakers. Audio CDs, however, can only accept 16-bit audio, so the sound will have to be converted. While 24-bit audio will sound better, there are limited playback options for song files in this format.
An advantage with 24-bit audio is that it has 250 times the audio resolution as a 16-bit standard audio file, but 24-bit audio takes up more space. When you are limited on space with a hard drive or other recording device, it may be best to use 16-bit audio to save space. For every gigabyte of 16-bit audio, you would need 3.25 gigabytes of space for the same audio recorded at 24 bits. If space is not a concern, using 24-bit mastering techniques will allow you to hear the full dynamics and quality of the sound.
In the end, if you are planning on burning your music to a CD or you want to release it commercially, 24-bit recordings offer no advantages and also add another step to the process. The audio masters must be ultimately converted to 16-bit for use on an audio CD. This process reduces the bit rate, further diminishing the quality of the audio. Although most people would not notice the difference between 16-bit and 24-bit masters, the difference is there.