Late to the thread here, but I gotta chime in because I've been super disappointed with some of the more popular brands lately. Honestly, I bought a bunch of those Lexar Professional 2000x UHS-II V90 cards and unfortunately had one just completely die on me during a family shoot. Not great for the heart rate, really. They are fast when they work, but I dont know if I trust them for a high-stakes Seattle wedding after that happened. If youre worried about reliability, heres what Ive been looking at instead:

• ProGrade Digital SDXC UHS-II V90 128GB

These are basically my go-to now. They arent as flashy as others but the build quality feels way more solid than my old Lexars. The cards havent given me a single buffer hang yet during heavy burst shots.

• Kingston Canvas React Plus UHS-II V90

Surprisingly good for the price. Skepticism was high because theyre cheaper, but they actually keep up with the R6 II burst rate pretty well. Definitely worth grabbing a few as extra backups. The ProGrade is definitely the safety first choice tho. It sucks when gear fails, especially when youve got a huge deadline like this Saturday. Just make sure youre using both slots in the R6 II for redundant backup! Youve got this, Seattle weddings are gorgeous even if it rains...

Stick with SanDisk Extreme Pro UHS-II V90 for rock-solid reliability. Ive used them for years. If you need faster clearing tho, Sony SF-G Tough UHS-II V90 is practically indestructible.

Like someone mentioned, some brands are failing lately... are you shooting mostly bursts or video? Maybe try Angelbird AV PRO SD MK2 V90. Just be sure to format in-camera every time.

Bump - same question here

To add to the point above: I am quite satisfied that this discussion is happening, as I have been encountering the exact same issues with my R6 Mark II for some time now. It's honestly been a struggle to find a card that doesnt fail when things get busy.

• I have methodically tested several of the major brands mentioned here and I am still facing the same buffering bottlenecks.
• While I am generally happy with the camera performance, the lack of card reliability is a significant concern for my professional work.
• I havent found a brand comparison yet that provides a definitive solution for these high-speed write errors and it is really starting to affect my shoots. I have been dealing with this for about three months and honestly, nothing seems to work well consistently...