The Supercard DSTwo the more recent and actually in progress now emulates the GBA and other what-not better. But the EX4DSi http://www.ex4ds.com/product.html is also capable of emulating GBA roms and viewing movies due to it's RAM. (This was previously stated wrong and I edited as of the 24th)
My bad I'd always thought of it because on the flashcart itself it says "Revolution for Ds" which is also featured on the R4. Besides this post was to compare flashcarts and see if it is better. I just worded it wrong.
Sounds good but I'd rather the supercard. Reason why is because it's an established product, I rather something that has a name-this one I never heard of before and no idea how the support/compatibility with games is gonna go.
most flashcards can show movies even r4 Post Merge: [time]1277552104[/time] so it dosent need movies to be converted theres a homebrew app for that