IMO, the most important thing about a figure, at least for most Poser users, is "content." Popular figures are made not because they're awesome technical creations, but because they have tons of content. V4 is still very popular because it was around for so, so, long and tons of content was created for it. It is, however, a very good figure with lots of geometry to play with, which makes it an excellent figure for morphs, which ends up with V4 being able to have many distinctive, custom, morph features, turning it into just about whatever one would want...  In other words, not only does it have a huge selection of content, it's a figure that is very customizable. With either it's standard Poser rigging, weight mapping, or custom channels/morphs/ERC, V4 and its derivatives are, IMO, the most versatile stock human figures for Poser right now. And, that makes V4 "the best" choice right now, IMO.

That will change over time, though, no matter how a future figure may compare, technically. The longer figures are available and the more content that is created for them, the more popular they will become. But, "popular" doesn't always mean "better", at least for Poser figures. With the limitations and issues surrounding the G series in Poser, V4 still compares admirably and holds her own, IMO, no matter how many iterations of the G series are out there. Only when G series performance matches DS specs in Poser would V4 be threatened. Oh, and only if G series content starts to overwhelm V4 content, which happens to be something that appears to be happening, these days.

For myself, all I want is a good, versatile, figure that can be used as a good standard base model for customization and content use, if I happen across anything cool. V4 fits that bill, for me, and I haven't seen anything that comes close. Mesh density is important to me. It may not be important to others, though.