I have both programs on my PDA. Davis Drug Guide gives more in depth information such as nursing implementations, family/patient teachings and assessment. The problem with Davis drug guide is it does not have certain drugs listed in it, although it is rare. When that happens I use Epocates as a backup and I can usually find it there. If you're interested in Davis drug guide it can be downloaded on a trial basis through Skyscape.com. You can then evaluate it for yourself. Most of the programs at Skyscape can be downloaded on a trial basis and then fully unlocked if you decided to purchase them later. Yes you have to pay for them, but I found it better than buying a bunch of reference books and having to carrying them around.