i have that one as well (actually have 2 m3 perfect for gba), patching software works just fine, i am using windows 10 64 bits i have no issues with the m3 manager
i also have an old ez iv, and for the SDHC support alone it is worth it... i putted a big card with all the gba library and done..
the omega would give you several advantages like the sdhc support,
standard .sav save format, RTC was fixed (your m3 has rtc but every game uses the same clock)
fast loading (the m3 is fast enough anyway)
but at the cost of battery consuption, i don't know how much the m3 consumes however..
the omega is a good modern upgrade but try to look and see if the battery consumption gets resolved
as for the everdrive x5.. heh, sadly it is huge :C and also has the rtc problem..
but still you get sdhc (and i even think sdxc)
and i can't say more advantages or disvantages because i dont have one and didn't look in detail at it
but you know the m3 is a great card, i love it.. it has some stuff no other got...
(the nds mode in the ez iv is deprecated in new firmwares) it can work as a nds flashcart for ya ds
the only bad thing IMHO about it is really the no support for cards above 2gb :C
there is some docs saying it can work with 4gb cards but heh, i never managed to make that work
PS random chat:
jeez, the memories of wanting a gba flashcart with RTC and people talking about the m3 perfect, and then go like "impossible to find nowadays"
and it was really fucking hard for me to find one.. i remember going in rampage looking for it lel.
then much later the everdrive and now the omega happened, and kek..