Obviusly to use only 1 mSD card instead of 2. "One with All Consoles Games" v.s. "One with DS, Gba, etc. and one with 3ds"...
I think that spending effort and money on ONLY one mSD card is better that spending on 2.
So, i think he is asking if he can maintain both launchers (Gateway and Supercard) at the same time, or they can interfere one with another (errors, etc.)