Hi
Both DEPT and INEPT are polarisation transfer NMR experiments, meaning that they uses the population difference for a nucleus with high magnetogyric ratio (ex hydrogen) and transfers this to a nucleus with low magnetogyric ratio (ex carbon). The difference is that for INEPT the pulse angle is dependent of the chemical shift, while for DEPT it is not. So DEPT is a easier experiment to run, and much more common.
-M