default format for SDXC (up to 64gb) is exFAT and has different architecture, people that says is compatible i don't think is the real deal.
By the way Buying a SD Card with UHS-I techonology imho is waste of money, the 3DS wont read GateWay 3DS at 60~100mb/s
Another thing. You guys should ask to gateway the max speed that the gateway flashcart reads the SD card...
By the way read speed only makes difference it supports UHS techonology, because will read up to 40mb/s.. but THIS if the flashcart/3DS actually supports.
If not, wont make any difference buying a class 4... a good Class 4 SD can read as fast as a class 10....
Understand, the CLASS of a SD Card is to determinate its speed for its Writing, not Reading.
The only notable difference is with Fake SD cards that usualy are slowers, a hardware with UHS support(need a SD with UHS techonology tho)
OR if the device you're using is to write data.
I dont think the gateway flashcart writes anything to the SD Card. No problem buying a class 4 that is much cheaper, and usualy people think is fake by its price lol
But if it could supports UHS would be for sure better buying it...
edit:
If you'll use for High-end photographic hardware, or wanna use in a near future for your smartphone it's ok tho,
but remember that only few cellphones supports SDXC and UHS techonology, old photographic hardware also.
I don't know why people don't look around about what they're buying. The worst is when they say:
"My smartphone isn't reading fast!" lo l clichê