None, you can import ANT projects in Eclipse though, the SDK projects are normal ANT projects.
You can do it the other way around though and import your eclipse project and assets folder to only edit assets in the SDK, use File->Import Project->External Project Assets for that.
Theres no reason to use Eclipse with jME though, the SDK can do everything Eclipse does and you can even set your keyboard shortcuts to the Eclipse layout.
If you find a solution for something you asked for it is a good idea to post the solution as well, otherwise your post won’t help anyone searching the forum for solutions.