I still use V4 for the same reason I occasionally use V3 or V2, and keep thinking about using Maya Doll (there's never enough time in my days). I have particular V4 content I want to use. And since I can use the Morph Tool, my own materials, Poser's subdivision, and Blender's many sculpting and modeling tools, I have no problem using pretty much anything I want. That said, precisely because I can make my own content, I'm beginning to prefer Dawn. I've absolutely never found a figure easier to morph. Well, and I like diversity. Outside of Miki, she's been the best at morphing to African and Asian characters. And while Miki 1 is better at both, Miki 4 isn't as well supported as Miki 1. Miki 4 has a decent mesh (though her eyeballs could use some work), but her less realistic looks have made her more replaceable and less well supported.

I also like Dawn because she works in both Poser and DS. While I (personally) still extremely dislike using DS, and can't stand the fact that there is no documentation for about 90% of its features, including almost all of Shader Mixer, I really love using Iray. I got V4 WM to load and work fine in DS, but she mangled after closing the program and re-opening the scene. That was seriously disappointing.

To be very honest, my biggest performance shift has been from Firefly to Iray (so much easier, more powerful, and quicker) and Poser to DS (so much less powerful and more clunky, due to lack of dynamics and the Morph tool). I used V4, V6, G3, and Dawn, and the biggest issues were the limitations of the software. I didn't get wildly improved results out of V6, and didn't see any point at all to G3. Though I did appreciate how the many years of experience- and an infrastructure our money funded- has allowed DAZ to start a figure off with tons of morphs before you spend any money. I was surprised at how much I could do with G3 if I had wanted. I couldn't inject some morphs into V4, and as I said, DS inexplicably mangled V4 WM after handling her just fine for hours (losing me a substantial amount of work).

I'd use Roxie if I had the time to work on her steadily, or if I needed yet another thin, baby-faced female figure of Northern European origins. She's not bad, just not outstanding in any aspect. But who knows, maybe one day I'll see something for her I really want to use.