Moved the thread to the correct forum.....
The CycloDS is considered one of the best flashcarts available for the DS. What it has over an R4 is:
Real Time Save - Save anywhere, at any time in a game.
Better cheat code support.
An in-game text reader - You can copy and paste a text file (like a walkthrough) into the Cyclo and access it during the game.
Slow Motion - Mostly useless feature, but allows you to run a game in slow motion to make it easier.
Still supported by its team - The R4 has been dead for a long time now.
If you have a slot2 3in1 card, you can play GBA games without extra patching.
The firmware is actually flashed to the card as opposed to being just a loader installed on the microSD.
Supports SDHC microSD's. R4's only support up to 2gig microSD's.
I myself went from an R4DS to a CycloDS and have been very happy with it.
Here is the link to Team Cyclops....the maker of the CycloDS:
http://www.teamcyclops.com/
Unfortunately, their forums are down at the moment. They are working to fix it, but you can access the CycloDS part of the site to read the carts manual.
Hope that helps you.