A year or so ago, I wrote a blog post on why I switched from Nikon to Sony. A few people asked why I didn’t move to the Nikon mirrorless system. And the answer was simple, I didn’t want to risk shooting a wedding with a single memory card slot.
I shoot RAW to both cards at every wedding. And have a rigorous backup process once home too. I know lots prefer to have their backup as Jpeg, but if my main card failed, I’d still want to have the RAW files. That’s just personal choice. I just believe that shooting a wedding with no real-time backup whatsoever, is irresponsible when there’s no real need to.