The Acekard2i has served me well for many years on many different models. (DSL/DSi/DSiXL.3DS)
However, this latest flashcard block had me worried enough to get a Supercard DS TWO.
It is more complex than the Acekard 2i to setup and has a significant higher battery drain than the Acekard (due to the additional CPU)..
However,that said, it does have more features, and may be one of the few that will work with the newer Nintendo firmware.
If you do not upgrade your firmware (affects DS Shop mainly) I find the Acekard the preferred choice due to simplicity of updates and setup and the longer playing time.
The DS TWO is clearly a superior card but the additional features brings additional complexity. The battery issue is not bad but it is noticable.