I used to own a really tricked-out DRZ with RM forks, TAG triple clamps, white head pipe and Yosh exhaust
, racing cam, and flat side carb among other mods. The bike ran really well...almost as well as the KTM 520 EXC I used to own(well ok...not quite). The problem with the DRZ was that, although it makes a pretty dirt-worthy dualsport, they are still heavy compared to other bikes like the 520. On the road manners (mine was licensed)side though, I can tell you I hated the bike. Because I do like riding my bike to work now and then, the DRZ ended-up being sold.
After a 1.5 year hiatus without a bike I bought a used XR650L last year. Its workable off road, but pretty soft in the stock suspension department and seat. Kind of like riding a big sofa. It does handle 2-300 mile road trips over asphalt and gravel nicely though. It all comes down to what you need in a bike I suppose.
Personally, I would never buy another DRZ400 simply because its not great for dual sport road use, and in my opinion there are much better machines (like the KTM 525 EXC) out there for the more off-road oriented dualsport and trail use. The XR650L on the other hand is a nice all around bike, but the stock suspension is weak and the bike feels really tall and heavy. Its kinda boring too, but is a reliable and trustworthy steed. In the end neither option is perfect. Truth is there are always compromises with any bike. These of course are just my personal views, and I am certain not shared by everyone else.
Btw..I have owned a few KDX's and wish I still had one for trail riding!