My first flash cart was an XG Flash Lite 128Mb.
At the time I didn't notice the megabits stuff, so I was a bit frustrated because I couldn't fit more than 2 64Mb games but, hey, I could play mario golf.
The flash cart turned out to be a shit, the batery died and when I tryied to change it I damaged the sram, don't know how.
After thar I bought an XG Flash 2 advace that I have 'till today, it's working fine, the batery is changeable and holds more games.
For the DS I bought a DS-X. The first flash cart that didn't require a pass me device. I consider it's ok, and the only drawbacks are de size 512Mb and the lack of upgrades.
Now I have a DS One, it's a prety descent cart, but the upgrades are very scarse.