you can get super card and R4DS anywhere.. you just gotta search yourself.. i would definitely because it looks nice and it runs smoother.. Plus more people have the R4DS more then the supercard... the R4DS...
Why the M3 over the R4? Well, allow me to put in terms that everyone may understand. This is the same analogy that I use each time the "vs." question comes up:
Think of the M3 Simply as a name brand product, let's say, Tylenol Acetaminophen, and the R4 as a generic brand Acetaminophen (like a store branded Acetaminophen). Both contain the same elements (ingredients/components), both are manufactured in the same facility, and both serve the same function. The differences, other than packaging? The store brand is priced cheaper!
To put it in another way, the M3 is more popular because of brand recognition, R4 for the price. Guts, functionality, and quality is all the same.
Kernels (OS, Firmware, whatever you want to call it), are both updated one after the other, thus making compatibility issues game and TF card wise similar to both M3 and R4. R4 usually updates their Kernel before M3 does. Both kernels cannot be interchanged with each other(R4 kernel on M3 Simply, etc), ans also with language versions (Chinese R4 cannot use English R4 kernel, etc.)
Homebrew? For those wanting homebrew, This Page will outline what homebrews are compatible. It may not look like it, but both M3 and R4 have the same compatibility when it comes to homebrews. The M3 part of the wiki is just a little more well organized than the R4 part.
TF Cards? TF (MicroSD) card compatibility is roughly the same as outlined in the previous wiki, where the main game that has major issues is Castlevania: Portrait of Ruin. So, unless you plan on intently and intensely play C : POR and only that, then get one of the more highly compatible TF card. Otherwise, it really doesn't matter.
R4/M3 conversion? This can only be done with the 1st gen R4/M3 cards. The 2nd revision of the card only allows the language conversion from Chinese to English and vice versa. The 3rd revision does allow the language conversion, but requires a bit of effort to do so.
GBA games? No, there are no Slot 1 cards that will play GBA games nor is there an Emulator available that will play GBA games via Slot 1 card. Look into getting a Slot 2 card for such things.
source taken from
R4DS Vs. M3 Simply... - MaxConsole Forums 
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