Looking to get one for my GFs DS and wondered: What are the differences ? I am assuming the only thing is the HC runs SDHC cards better ? thanks
original r4 can only use micro sd. newer versions, and there are many, about 9 versions out there, all uses different firmware, can use micro sdhc. i suggest you look for anything that doesnt have a r4 in its name. goto http://gbatemp.net/?dynamic=8 for flash card reviews and pick one that have a Golden Award.
As MaryD7 has said the original R4 can only use micro sd cards (these as standard go up to 2GB, there were some 4GB but these are incredibly rare and very expensive) SDHC is a new format for the SD, these look the same but are incompatible with the original R4, a card that can run SDHC can run both SD and SDHC cards. Again avoid the R4 unless you want to be adding to the list of people here with issues and set up problems. When set up correctly most work with most games but set up can be a nightmare