And it is the YMMV part that is the problem. I have used two kidneys and two eyes and two lungs and two testicles for 56 years. Never have had a problem. YMMV. There are plenty of stories here about cards failing in critical use cases, but YMMV. As we say in the gun world: Better to have it and not need it, than to need it and not have it. A litigious Bridezilla is a, well, you know. Then again, people have to assess their own risks and make their own choices. There is no right or wrong, however, were I a wedding photographer two cards would be a must for me. Not being a professional, it doesn't bother me that my R has one slot. My next R will have two. I've not needed a spare tire for many years, but I am sure glad I have one.I've been using digital cameras, and other devices that use memory cards, since the 1990's and have never had a card fail on me.
I use a 5d3 for events and weddings and have never needed to use the second card.
Now also having an R, it doesn't bother me at all that it only has one card.
When it comes to data reliability, the fewer points of failure between where data are generated and where data are stored the better. Evidently a dual card camera is the simplest and safest solution - wireless technologies imply more points and requires also a to understand well the weakest points and design accordingly. 5G is sold by too much interested parties as the solution to everything everywhere, but when there will be enough users, it will be clear it is an improvement but not the answer to life, the universe and everything (that's of course, 42G).Maybe. So in the meantime, keep it simple and write to two cards if your work has any genuine value. Why is this even an argument?
I am sorry to read this. Can you recover at least some of your photos from the failed card? There are programs to do this and if there is hardware damage maybe a data recovery company could help.I had a Sandisk SD card fail today. I lost the morning’s pictures.
There is no substitute for a second card.
I imagine many more of us do the same but won't admit it in public because we have to be outraged about a single slot.I only use two cards when I'm on a paid job and when I'm on a very expensive vacation where I might not visit again. Otherwise for sports, nature, wildlife, etc I only use one.