Playing on the PC lacks portability and the gamepad, which is the point of GBA. In general, playing on the PC isn't a very complete experience.
There is no rechargeable battery for GBA flash carts. They all use CR1220 batteries which are not rechargeable. Rechargeable batteries for GBA flash carts is a myth and has been debunked in one of the forums previously.
The point about link cable for multiplayer is very true. I agree that many games rely on the multiplayer feature. Is there no way for the DS Lite to make use of the GBA multiplayer functions? If not, is then GBA micro the best console?
Im abit reluctant about the gameboy SP cause the top screen tends to break off easily
Is the M3 perfect better or the M3 DS with GBA expansion (the picture above, that thin DS lite sized cartridge)? Also, why is the M3 so good? It is such an old cartridge, are you sure it can run the newer games? And why did they stop making it >< EZ flash is still available but M3 is not
(dang it i really want to get 1 for myself)
Finally, are there any other special cardtridges?
My laptop is pretty portable and many current consoles have nice USB or bluetooth game pads. Portability is not really a big thing for me though -- in the vast majority of cases I play my consoles within reach of a USB port or a mains socket. Equally with the GBA being the return of the 16 bit era for a lot of things many games there were ones I played (or played the prequels to) in front of a TV/in front of my PC screen originally.
No way to do link cable on the DS (not even some crazy soldering stuff from what I recall). Give me a few months and a few thousand dollars worth of gear and I might be able to make an expensive and hard to do mod that approximates it but it is not going to happen otherwise.
If you like the GB micro form factor and screen, and don't care about GB/GBC, then yeah it could be the best for someone.
"There is no rechargeable battery for GBA flash carts... Rechargeable batteries for GBA flash carts is a myth and has been debunked in one of the forums previously. "
Probably not on any ones you will find today but here is a picture of my launch EZ4's PCB (battery side)
http://s2.filetrip.net/p/46/256201-EZ4 old and new comp 2.JPG
It uses a panasonic VL2020 which very much is a rechargeable battery --
http://uk.rs-online.com/web/p/coin-button-rechargeable-batteries/0407877/
The newer EZ4 (pictured above it) does not but hey.
SP top screens break? Since when? DS and DS lite hinges we see break and have to teach people how to repair all day long, the only ones we ever see for the SP are exceptionally well used ones or actual deliberate/accidental bending back.
Basically every GBA flash cart will run anything that fits on it, though you might need extra patches/a better save patcher than the teams provided originally -- GBA games have no real anti piracy (other than the nes classic/famicom mini which you should not be using when there are far superior emulators then there are a handful of dragon ball Z games that have it and not much else), no fancy special chips like the SNES, no odd quirks that trip up certain games and just a few games that have real time clock, a tilt sensor, a solar sensor or some kind of link device (think spyro skylanders, amiibo.... but for the GBA).
The GBA slot supercards, the team cyclops clone of the supercard and some of the very first GBA flash carts that were slightly tweaked GBC flash carts are the only real exceptions (they have low compatibility, slowdown, need for extensive patches....).
The M3 had 256Mbit of PSRAM (games were usually 128 or less but some went up to 256), has a real time clock onboard, has a reasonable loader with some fancy features and supports external memory.
Note do not buy a M3 professional for your GBA purposes. Similarly do not get an EZ4 lite compact or a supercard rumble.
It is old but so is the GBA and as well as there being no real issues facing GBA games there was nothing new that happened in the GBA world, as far as anti piracy and new save types, for a few years before the end of the GBA lifetime and quite some time before the M3.
The EZ4, which is the best GBA flash cart that you will easily be able to find at this point in time, also has external memory (these days it even does SDHC). However it has a slightly lesser loader (no real time saves/savestates, cheats are better served using trainers or GBAATM, soft reset is a bit iffy, sleep support is not much better) dropped real time clock (only really used in pokemon, boktai and a couple of other games that even fewer people care about), the main model you will find only has 128Mbit of PSRAM (the rarer EZ4 lite deluxe has 256) so if you want to play larger games it will need you to flash it to the EZ4's NOR section (slow to write but it stays there until you delete it unlike PSRAM).
The EZ4 will still be able to play basically everything though so people tend not to mind too much. The 256Mbit of PSRAM and the RTC make the M3 an objectively superior cart, how much this matters is up for debate.
No idea why the M3 team stopped making them, originally they were not designed for the GBA but for the DS (we used to run DS games from GBA slot carts) and just so happened to have GBA capabilities too. When DS slot flash carts appeared then people moved to those (they were easier to work, often cheaper and easier to maintain for flash cart teams), all the kids had long given up on the GBA as well and it is only somewhat recently that we have seen people get back into it in a big way, or at least getting back into it and not wanting to just use one of the readily available expansion packs for the DS/use original GBA hardware. To that end I guess it was not worth it financially and they stopped making them.
I did cover all the various games with extra hardware or anti piracy on that link, along with what can be done to run them if so. On the rare occasions I learn of anything new (usually some Japanese title, recently it was one called plaston gate), or if there is a new patch worth knowing about then I add it to that list.
http://gbatemp.net/threads/buying-a-gba-flash-cart-in-2013.341203/page-18#post-4756995 to save you scrolling back up.