1 Quality work Not from china.
2 High compatibility within the 95-99% conservative estimate
3 no need to patch the roms using dodgy software just drag and drop the raw roms into a sd card
4 Real save memory types all compatible games will save properly they will then be copied to the SD card
5 even the phat model has low power draw compared to the older flash cards meaning alot longer battery life
6 RTC support for those that use it like pokemon.It is also 100% replaceable and all batterry saves are placed on SDcard like the rest
7 Fast flashing of the rom it doesnt take 30 seconds to flash the rom from the sd card to the onboard rom chip.
8 homebrew/emulators are bootable
9 not advertised but rom hacks will work its an lesser talked about unofficial feature
10 A good amount of OS updates a direct support forum to the maker and a good warranty,and program diagnosis roms to check all the major components if you feel like DIYing it should something break or just to give more info on the issue.
Also for those wanting savestates planned on the X7 everdrive will have it unknown if what else he will add to that the gyro and light sensor has been mulled about but given he was able to shrink the X5 the x7 might not be as big as he feared it would with all the crazy things the GBA carts tacked on.
1) The M3 was a solid little flash cart family on the GBA. If not having it made in China is a thing then OK.
2) Compatibility is the same for most things that are not supercard or a clone thereof.
http://gbatemp.net/threads/buying-a-gba-flash-cart-in-2013.341203/page-18#post-4756995
Unless they are going to do something like make those Shrek videos work, stick a tilt sensor, stick a light sensitive device to play boktai, or spend all the time and effort to get that GBA personal organizer there really is nothing in it.
3) That would be a perk over the M3 at least. Drag and drop is pretty common right now though, and I am not sure it counts as an absolute huge win as most of the save functionality was easily replicated by other means.
4) A nice feature and way I would design a modern cart but more or less kicks the battery issue to the clock. It is not like saves before could not be fired around between flash carts, emulators, real carts and beyond.
5) I will have to find numbers here, and don't have any for the M3, but some of the older stuff was in the official cart or sub official cart range.
6) The GBA slot M3 was one with RTC. The EZ4 line was the one that dropped it, also there are patches that get most of the way there. Not having to solder when the battery might die in a few years is nice too.
7) A minor perk but a perk never the less.
8) From the cart itself? A nice feature if GBA emulators are still your thing.
9) The only ROM hacks I have seen that will not work (assuming they fit on the cart in the first place) are ones that will not work on hardware in general and also some emulators, this usually being when someone makes the hack using an inaccurate emulator. No flash cart is going to change this.
10) M3 do seem to be a bit absent these days but as far as problem ROMs go then for the most part that was all over probably around the time we got the last EEPROM save type (there was one before but most met it with a Harry Potter game), which is to say ancient even when that now ancient 2013 post above was being made.