I have and love both. I briefly considered selling 1 because I didn't have space on a 2nd board for another large format box.....but I fixed that problem

It's almost impossible to do a comprehensive demo of these......depending on the gain staging & bass there is an enormous variety of sounds available in both, as well as a lot of potential overlap. Both will give you 2 channels with separate eq and depending on the tubes you fill 'em with, any of their 4 channels can be run very clean right through purt durn filthy. The most significant feature difference is the Fender tone stack on the DC vs the HiWatt stack on the Detective. Best to look at the on line tone stack simulator which has been linked many times in this thread and play around with it. That said, if you want to have 2 tube flavours available in 1 box, either will be delicious, pretty much regardless of your taste, as long as you take sufficient time to get to know the pedal in order to optimally milk it for your aural pleasure. Also, just to further complicate matters, a lot depends on what (if any) other pedals you'll put in series with these. For example, I also have a JC Emerald. It's great, especially for overdriven sounds, and has a very nice high/mid/high end.........but after having it around for a while one day I paired it with my SA Zio pedal and the 2 of 'em complement each other perfectly and together sound amazing....even better than either one does alone or in any other combo I tried.....it was a sonic lightbulb moment. It's a lot like experimenting with spices in the kitchen, or ingredients behind the bar. You won't go wrong with either, and your best friend is the time it'll take to really get to know whichever you choose.
On an unrelated note, the youtube demo of the JC Emerald is crappy and IMHO should by "unlinked" from the S-Box site. It was done by 2 guys who are not into dirty tones. They barely scratched the surface of its' palette. I find it's misleading and inappropriately non-flattering. That review is like asking someone who hates spicy food his opinion of Tabasco.