Speed issues:
The read/write speed is dictated by the microcontroller speed on the SD card itself. Here is a good explanation of SD Cards
Can’t be stated for sure. With cheaper card, FAT16; with some high-end ones,
FAT32. Read http://pocketpcmag.com/forum/topic.asp?TOPIC_ID=17921 , it
explains everything.
Esentially the fewer clusters of the card, the faster it will read and write.
Fat16 vs. Fat32 performance tests http://www.geocities.com/SiliconValley/Peaks/9892/fat16vs.htm