So the bottom line is: When you re-format your card, even to exFAT, chances are very, very high that it doesn't work as well afterwards as it did with the pre-formatted file system. What's worse is that there's no tool that will tell you: "Ooops, something went wrong, block alignment isn't perfect on this card." You'll just keep using a card that is slower than what you paid for and will wear out sooner. So I'd prefer not having to do all this again.