What happened in 2018? Is the reform the way to go?
The EZFlash Omega was released, and generally got up to speed.
The Reform is an older EZFlash product and while it, along with just about everything they did before, is "if it fits then it runs" (give or take various amounts of fun and games from the likes of
http://gbatemp.net/threads/buying-a-gba-flash-cart-in-2013.341203/page-18#post-4756995 ), the Omega has more features so would probably represent the better bet.
To that end choices are
Absolute top tier
Between the everdrive mentioned at the start and the Omega. The everdrive sticks out a bit, the omega gobbles a bit more power but they got that down (though not to original or the even better some really old school carts used) but feature wise they are the best we ever saw, and likely about as good as it gets until we start playing with replica hardware and twisting that. The Omega is considerably cheaper in most vendors.
Whatever was left standing prior to everdrive and omega. Again most things here are going to play just about everything with the tricky stuff being on that list. For many years all you could really find was the EZFlash 3 in 1 if you wanted to use it on a DS/DS lite and had a DS flash cart to manage it, and the EZ4. If you could find a good m3 or g6 though then it was good.
Said EZ4 was the last thing available in the dedicated GBA cart range for a while, and the EZTeam put out a few new runs of it, then a version with microSD instead of mini and finally the reform which is a sort of new but still essentially an EZ4 type device, which was then obviated by the omega. Other than the really fancy features it should be noted the EZ4 line lacks real time clock aka RTC which most like for the gem named pokemon games which have a clock onboard and use it for a few things. More on the link at the start for patches on how to sort that.
Older stuff.
Older NOR and NAND-RAM stuff from the GBA era was running GBA stuff like original hardware, or original hardware with
cheats, reset, savestates in some cases and hacks if you wanted them, for years and years and did not suddenly stop here. Storage capacity was smaller, many had batteries to sort or will need sorting if you found one, not to mention you will probably need Windows XP and some software fiddling, maybe also a serial port and special cable.
Supercard and the supercard clones (team cyclops made one, though there are others).
Supercard cheaped out on GBA RAM and thus what little it could run needed speed patches and other hacks. Because of this, and them continuing the support the DS side of things for quite a while, you could still find them from time to time.
The non GBA GBA slot devices.
As memory to make GBA games run is expensive then before we all went to DS slot flash carts the various flash cart makers made cheap versions with limited (ROM size rather than speed) or no support for GBA stuff. EZFlash's take was the EZ4 lite compact (the EZ4 lite deluxe on the other hand being one of the most sought after flash carts during the "only the EZ4 is available days" owing to it having 256Mbit of PSRAM and 384 of NOR).
Everything else.
This is mainly stuff like fire cards (usually 128MBit/16 megabyte NOR based things) and some of the really cheap GBA carts made, as well as most homebrew designs on such things.
