SuperCard DSTWO*
AceKard 2i**
R4i Gold 3DS***
* = Reliable, stable updates and can run GBA games and special homebrews. Feature-packed cart but costs $30-$40 depending on where you buy it
** = Reliable, stable updates and relatively cheap (I think I saw them somewhere for like $15-$20)
*** = Similar to AceKard 2i with reliable updates and taking in costs
So it really just depends on if you want extra features like more advanced homebrew and GBA games on your DS cart but costs a little more than other reliable carts. If you want reliability and lower costs you'll go with AceKard 2i or R4i Gold 3DS, but if you're willing to spend a little more you can get many more features, just remember _not_ to expect any DS carts to run 3DS games now or ever.