A very good example of differences, Lynne. And, PADI only recently changed their standards to allow helium on Dive 12 (last and deepest) of the Tec Deep course. Personally, I suspect that shift will continue to evolve, and helium will eventually be allowed in all PADI Tec courses, beginning at Tec 40. But, that will take time.Well, not exactly accurate. PADI teaches air only to 165', which is deep enough, certainly. And, some would consider GUE's early inclusion of helium to be a major difference, not a subtle nuance. I do not necessarily, but it was such a contentious issue that it may have pushed PADI in the direction of incorporating the helium option in Tec Deep, on Dive 12 as noted above.
There are a number of SB threads that debate the relative conservatism of the algorithms used in different dive computers. Suunto, in particular, sems to attract more than a little criticism, some of it quite vigorous, on the basis of how conservative the algorithms used in their computers are perceived to be. In some ways, PADI is the 'Suunto' of dive training. They are conservative. They didn't move into nitrox quickly (as several posters have noted), they didn't move into technical training as early as some, they don't allow helium as early as some, only now are they moving toward Cave training. Like Suunto, they are not conspicuous risk takers. So, if someone wants truly 'cutting edge' - the absolute frontier-moving training course, they should probably look to an agency other than PADI. That is not a criticism or compliment to PADI or any other agency, and doesn't mean one agency is 'best' or 'worst', going back to the topic that strated this thread. Rather, there are some differences that divers should consider in selecting which agency to train through.