jim16127 said:
Even thought they are out of date the team behind them still releases firmware updates for them to keep up with the new problem games.
Being out of date means they don't receive the proper updates they should. The M3 team has not released a patch for the M3 cards for about three months, the previous update was in September, then they went "dead", and the new one was only released recently, 17 Dec - and still many games have not been fixed in that patch. Although a new patch is said to come out in January, they said themselves they will have the Chinese holiday, so it will take some time before a new patch comes out after that. Plus they can go "dead" again, and although I'd love if they patched all games in the Jan. update, they might or might not. So that's why people tell you to buy another one. I'm not sure how it goes with Cyclo, but I since others say it's also outdated, it probably doesn't play all the new games as well like Acekard or DStwo do.
DSTWO has all the features of M3 and unlike M3 you can run on it almost every game without a patch, so if you want best game compatability and all the features like slow-motion, multiple saves and so on, go for it, because you have to rely on unofficial firmware to run new games on the M3 (that is, when those firmwares like Wood get updated), which however do not support real-time saving, slow motion and other things. Plus DStwo has built-in GBA emulation, and you an always use the 3-in-1 EzFlash expansion to get better GBA compatability with rumble, like it was mentioned above.
So my advice is also DStwo - it wins over all cards in compatability, lots of functions which you'd like like RTS or SM, it has good support of emulators (some of which are exlusive for that card) and inbuilt GBA+compatible with 2-slot expansion pack.
Or you might wait for the iCyclo and see how it's like.
EDIT: Evo.lve beat me to it.
He summarises my two main points in less words - M3 is not really up to date anymore, and DStwo is good despite whatever you may have read, those bugs were fixed. That's why people love it and it's so popular. //and I fixed some typos in the post.