Hi Kevin,
Both titles are very useful for learning and practicing the Taoist breathing techniques. The Longevity Breathing DVD focuses primarily on the physical mechanics of whole-body breathing. The Taoist Breathing CD Disc 1 corresponds to the breathing exercises in the Relaxing Into Your Being book, and also covers basic principles of energetic breathing. Disc 2 takes those lessons to the next level. These CDs also have chimes at intervals designed to help you increase the length of each breath.
I remember Bruce once mentioning that if you are primarily interested in health, practice the physical breathing first; if you are primarily interested in meditation, practice the energetic breathing (i.e., nose to central channel to lower tan tien) first. The other important thing to remember is that the physical breathing enhances the energetic breathing, and vice versa.
Breathe well,
Don.