I'm currently training to be a PADI instructor and am looking at doing a Nitrox course during our holiday break. I can choose between PADI or TDI with the dive shop that I will do the Nitrox course with. Is there any reason to pick either one of these courses? The shop prefers to teach TDI. If I do the TDI Nitrox can I still count them as Nitrox dives towards the PADI specialty instructor rating once I've certified the right number of divers?