Supercard DSTWO has the potential in overthrowing AceKard if their GUI get's better, faster loader times ... and if it has iPlayer abilities ( No decoding for RMVB, MPEG,MP4 ... etc)
Anyways, there's a difference between AceKard 2.1 and AceKard 2i. 2.1 is revised version of 2 and it is only compatible with the DS and DS Lite. 2i has the compatibility of being played on the DSi, and is 100% compatible with the DS and DS Lite; for the 2i to work with the DSi, you need to flash it for the 1.4 firmware. With AKAIO 1.6, all games will work ( try and stay away from the official firmware since most game updates don't happen frequently ).