Derkie, I don't really know how good the DS Xtreme is but so far its been getting positive feedback from people who tried it out (
http://www.maxconsole.net/?mode=news&newsid=10212). Not having to get a separate Passme device for it is reason enough to get it, and the faster transfer speed is also a big plus. However I don't know how it fares on homebrew software (might not be sucha big issue for some) and you're limited to just 512MB. Also I don't think it'll be cheaper her bai, and it probably won't be available here anytime soon either (I was actually surprised to find memory adapters / passkey devices for the DS).