FWIW, the DCS WiFi Companion is really the latest information and includes most or all of the information that's in the DCS Companion. Before he passed, Barry had stated he would no longer be updating the DCS Companion but rather just continuing with the DCS WiFi Companion.
If you get a killer deal on the DCS Companion 3rd Ed. that's OK, but if you're paying retail, go for the DCS WiFi Companion 2nd Ed.