It depends on your knives. The Sharpmaker is a great tool, but it won't do much for you if you need to remove a lot of steel. The ceramic rods are just too fine. It'll put a scary edge on a knife that still has a bit of an edge, but you'll be there for days trying to reprofile a really dull knife.
There are diamond rods for the Sharpmaker, but they cost more than the basic set. You can however use coarser sandpaper glued or taped to the standard Spyderco rods to do heavier reprofiling. That way you'll keep the 30 or 40 degree angle that the Sharpmaker uses.
It has its limitations, but the Sharpmaker is probably the best sharpening system on the market. That said, since you have the Lansky, if you get good results with it and like it well enough, just stick with it and get the diamond stones.
How do they compare to ceramic? Diamond, even in a fine grit, will remove a lot of metal very quickly compared to ceramics. My experience has shown that a diamond sharpened edge will be toothier and good for heavy cutting, but it won't slice that evil news paper or shave hair off your arm. But if that's the edge you need, then it may be just what you're looking for.
Or, if you have the disposable cash lying around, get both the diamond stones for the Lansky and a Sharpmaker. Grind the edge on with the Lansky and keep it there with the Sharpmaker.