I have and use both the DoubleStuff and the DC4. I like both, for different reasons. The stock DoubleStuff is a finer ceramic, on both the 'medium' and 'fine' sides, than the ceramic of the DC4. I like the DC4 because it's more aggressive on the ceramic side, and will put some 'bite' very quickly into the edge. And obviously, the diamond on the other side of the DC4 will do a pretty quick repair job on a damaged edge, if need be. Used by itself, it will leave a very good coarse working edge. As a field hone for any or all situations that might come up, I'd probably choose the DC4 first. It'll definitely maintain an edge with ease, and would be more useful if you had to fix/repair a really damaged edge in a hurry.
The DoubleStuff does a better job at polishing an edge (or very nearly so). It's ceramic is the same as the medium and fine rods of the Sharpmaker. By itself, it's probably too fine to do any major repair on a damaged edge. For light touch-ups and burr removal duty at home, I use this one all the time.