Which flashcard should be the best for your 3DS/2DS/DSi/DS?

It will be a bit confused for new users of flashcards as there are too many kinds of flashcards can be selected, and they are from different developers, with various software and functions, even same cards have different versions, so which one should be the best for your consoles? A guide or a recommend will be needed. Maybe below information will help new users:

For 3DS,3DS XL consoles:
Real 3DS flashcard:
The Real 3DS flashcards have been available now, they can work with 3DS console to play 3DS Roms in 3DS mode.
Gateway 3DS is the world first real 3DS card which start selling on the market on end of Aug.2013!! The new 3DS cards make users to enjoy real 3DS roms with their console.

Gateway 3DS Card

3DSLink and R4i Gold 3DS Deluxe Edition came out on the end of Oct.then. All of them now just can work with 3DS V4.1.0 to V4.5.0, two cards will be packed together, one for set up and another for playing 3DS Roms. Both 3DS and DS games are supported,all Nintendo consoles are workable! It is great news for the 3DS flashcard users, but if your 3DS have been updated to higher firmware than V4.5.0, these cards still not supported.

R4i Gold 3DS Deluxe Edition Card

3DSLink Card

R4i 3DS:
R4i 3DS card should be the most popular 3DS cards before the real 3DS flashcard coming out. A lot of different R4i 3DS card are selling on the market, but the most popular items should be as below:
R4i Gold 3DS RTS

R4i Gold 3DS RTS Card

R4i SDHC 3DS RTS

R4i SDHC 3DS RTS

R4i Gold Plus

R4i Gold Plus Card

R4i-Gold Pro

R4i-Gold Pro Card

R4i Dual core

R4i Dual core Card

All of them work with latest 3DS V6.3.0-12,2DS V6.3.0-12, DSi V1.4.5,DS, DS Lite and any lower versions! Upgrade is available for each of them. They allow users to play 3DS, DS games in DS mode.
Supercard DSTWO:
A different card with stronger CUP, support all Nintendo console with latest firmware, GBA games can be played with software install in. This can be used to play DS,GBA games in one console.

Supercard DSTWO Card
For DSi,DSi XL consoles:
Frankly, all above cards which work with 3DS consoles can be used for DSi.But if you just want to choose a card for DSi or DSi XL, no need to use for 3DS, then R4i SDHC should be the best choice. R4i SDHC V1.4.5 is the latest version of R4i SDHC which support DSi, DSi XL V1.4.5 firmware and can be upgrade as well.

R4i SDHC V1.4.5 Card
For DS, DS Lite consoles:
R4 ds is the first flashcard in the world, it is the original one but just can work with DS and DS Lite with max 2GB memory card supported. R4 SDHC is the upgrade version which can work with SDHC microsd card. M3 Real work with DS,DS Lite but also can play GBA games.
For DS users, above all cards can be used but R4 DS, R4 SDHC,M3 Real will be much cheaper choice.

R4 SDHC Card

R4 DS Card