I've only had my 128gb for today and to be honest it is painfully slow, .cia's take way longer to install, takes longer to load and also more annoyingly, loading things like OTPHelper the borders/button prompts load but the actual options take anywhere from 10-20seconds to load.
Maybe I've formatted it wrong but it was a decent samsung card directly from amazon and its on fat32 with 32kb cluster
Maybe I've formatted it wrong but it was a decent samsung card directly from amazon and its on fat32 with 32kb cluster