If you just want a card that works for everything without any fuss, get a 128GB UHS-II V60 card.

> I need something fast enough to handle the camera's capabilities without bottlenecking. Ok so, since the a6700 only has a single card slot, you realy want to prioritize physical reliability so you dont lose a whole day's work. Honestly, I'd skip the budget stuff and go for the Sony TOUGH-G series SDXC UHS-II. They're basically indestructible because they dont have the flimsy plastic ribs or that annoying write-protect switch that always breaks off in the slot. If those are too expensive, the ProGrade Digital SDXC UHS-II V60 Gold is a great alternative. Just keep in mind that if you want to shoot in XAVC S-I (All-Intra) for the best quality, you'll definitely need a V90 rated card to avoid the camera cutting you off mid-clip. Not 100% sure but I think some 4K 120p modes might also require the higher speed class. A lot of people underestimate how much heat these high-bitrate files generate, and cheap cards can throttle or corrupt when they get too hot. Stick with a proven brand that uses high-quality NAND flash for peace of mind.

ngl i think everyone has covered the big hitters but before giving more advice i gotta ask... what specific bitrates are you planning to hit?? if youre doing 4K 120p at 10-bit its a totally different ballgame than just casual 4K30. im not totally sure about the current market landscape for the a6700 specifically but iirc some people have mentioned that certain newer brands are actually outperforming the old staples in terms of sustained write speeds. here is what im seeing from a market research perspective:

• brand consistency seems to be shifting as some manufacturers change their internal components without changing the model names
• i dont know if its true but i heard some users on other forums say certain cards run way hotter than others in these small aps-c bodies
• the price gap between v60 and v90 cards is closing fast so it might be worth checking if the premium is even worth it for your specific workflow id honestly check your video settings first because that dictates everything about the card choice!!!

Ok so, I have been through the ringer with various cards over the years, especially when I started pushing higher bitrates on my mirrorless setups. One thing I learned the hard way is that even the best cards can glitch, and I have become a huge advocate for the DIY approach to card health management. Instead of just plugging them in and hoping for the best, I always run my own stress tests and block-level checks on my workstation before a major shoot to ensure the NAND flash is actually performing to spec. Honestly, knowing how to use data recovery software yourself is a lifesaver if a card ever acts up because sending it out for professional service is expensive and takes forever. Regarding brands, I have actually been moving away from some of the bigger names mentioned here. I would suggest looking into Kingston. Just get any of their higher tier cards rated for high-end video and you cannot really go wrong. They have been super consistent for my workflow lately. I also think it is worth looking at brands that cater specifically to the digital cinema market because they tend to prioritize sustained write speeds over peak bursts, which is exactly what you need for that 4K 10-bit video.

I've been using theSanDisk Extreme Pro 128GB (V30/U3) with my a6700 for about 6 months now and it's been rock solid. Handles 4K recording without any dropped frames, and the write speeds are fast enough that I rarely see the buffer fill up even when shooting burst mode with RAW files. The 128GB gives me plenty of room for a full day shoot without swapping cards.