Which one is the best?

I'm confused to choose which one is better and can be used for my Nintendo 3DS, R4i SDHC 3DS, Acekard 2i or EZ Flash Vi. Where can I download the kernel (the folders to be inserted to the micro sd card which are for the OS or software I think, used to access the flahcard in the DS) for these flashcards for Nintendo 3DS? I have an EDGE but it can't be read at my Nintendo 3DS and do I need to replace my EDGE with any of these new flashcards or just replace the kernel with the new kernels for any of these new flashcards? Thanks