These are always interesting discussions. I show my rescue diver and nitrox certs, that's usually enough for whatever I need. It is interesting to me, that the rescue card seems to be more magical than other cards in the past.
It makes me think about training, experience, and a dive op's position on the magic of c cards:
A friend of mine has about 100 dives... (with AOW) all on one luxury Live aboard in the Bahamas. Many people consider that alot of experience. But think about this: she rents her gear, they handle it, set it up, take it down, and do everything for her. In the warm Caribbean waters.
My son, with 60ish dives (and only junior OW), has been in warm and cold water, fresh and salt, cavern, spring, good and bad vis. Shore, boat, night, day, etc. I mandate that he sets up and carries all his own gear, switches his own tanks, and checks his own gas levels (he does have nitrox cert). He carries an extra mask and often does his safety stops upside down with mask off (this is when we practice drills).
Despite his c card, and compared to my friend's certification and training, I'd humbly offer that my son is a far more experienced and better diver than she is.
In Sri Lanka last month, we were not allowed to dive any thing deeper than 50 or 60 feet, whatever it was, bc of his "inexperience". After the first dive, the DM told him, " dude, you can dive whatever you want, you are way better than most AOW divers."
The cards, as we all know, are just legal excuses for dive ops to manage liability.