For NTSC, I believe there's a small problem on shooting DV with the HVX- people are reporting significant aliasing on the edges. In the Pal camera (which I own), tough, that's not much noticeable.
I have yet to run tape through our HVX, so I still don't know how that would compare with the DVX, but if you can shoot on P2, you have the option of shooting DV50 which will look stunning by comparison. I've recently been shooting a short on my personal DVX (couldn't use the office camera), and it's been a little dismaying. DVX footage looked so good a year ago . . .
The DVX is about 1 stop faster than the HVX, and in 60i it's two stops faster (meaning the footage will be noticeably brighter than the HVX's footage). And in 480/60i, the stairsteppy edges are pretty noticeable in the HVX, much cleaner in the DVX.
Other than that, it's pretty much all HVX all the time, it's better for 24p and 30p, it does DV50, it has a better/sharper lens that gives you wider wide-angle and more telephoto, and it delivers much sharper 16:9 footage.