If you have a DS Lite ,Acekard 2i is a great choice , it has any emulators, but get a R4/AK2i + Ez 3in1 , after all the AKAIO/WoodR4 also can work perfect GBA emulation and all DS games. Plus there are millions of available skins online that you can download! Supercard dstwo has more features than AK2i (On-board CPU/Ram, GBA emulation, Snes emulation, video player ,ect) , it's own SNES emulator (that is better than the ones available to ordinary flashcards), Real Time Saves, Cheat generator, in game guides and lots of it's own homebrew. But it sucks battery life because of the extra CPU on-board. Back to our main topic , which one is better ? the only answer I can give you is : It all depends on what you want to use your flashcart for , and whether it is worth the extra money for a Dstwo. If you want to play just DS games, get a AK2i is a better choice as they are far cheaper than the dstwo . (such as this one： http://www.usar4.com/others-acekard-2i-flashcart-for-2ds3ds-xl-3ds-dsi-ds-lite-p-14.html ) You could get a Supercard DStwo if you happen to want to play emulated GBA and SNES on a DS(i), want to enjoy more features , Supercard dstwo is a better choice .(such as this one http://www.usar4.com/dstwo-supercard-dstwo-3ds-flashcart-for-2ds-3ds-xl-3ds-dsi-ds-lite-p-2.html )
supercard dstwo is the best option, got mine from http://www.r4flashcart.com/10-supercard-dstwo-flashcart-for-3ds-xl-3ds-dsi-ds-lite.html and never any problems. the acekard 2i used to be a good card, but the official team gave up on the card.
acekard 2i has stopped upate for ages,so if all you want is playing gba games ,dstwo is your best choice, but this price is expensive. But if all you want is playing nds games or homebrew,then suggested you buy r4i gold like this : http://www.modchipfactory.com/wood-r4i-gold-3ds-flash-cart-for-3ds-xl-3ds-dsi-and-ds-lite-p-1.html , top game compatibility and the price is hard to beat .
Acekard 2i is a great card, but acekard team stop supporting the card for a long time, so, the firmware hasn't updated for more than one year. If you need a flashcarts for DSi, DSi XL/LL , DSTwo is the Best choice, can supports all version DSi consoles.
