D|S is still in a state of flux at the moment and needs some time (years?) under its belt to settle down and decide what it's going to do.
In the long run, it'll probably be at least the equal of Poser if not better. After all, DAZ is the major content provider and it's in their own best interests to make D|S as good as it can be.
D|S can't handle dynamic items at the moment, though it's almost certain it will- or at least implement its own version- in the future, so if that's important to you now then you may want to get one of the Poser versions.
Poser's Firefly renderer is more advanced, more flexible and higher quality than D|S's 3Delight renderer at the moment, but bear in mind that 3Delight is constantly evolving and will probably surpass Firefly as time rolls on. It's also- arguably- easier to use.
D|S isn't so good at animation as Poser yet, but it's coming along nicely with each release.
Poser has a "weird" user interface where 3D programs are concerned whereas D|S has one that seems more "natural" for users of other 3D programs and is- arguably, again- easier for a first-timer to get to grips with. Still and all, neither of them is as straight-forward as perhaps they could be.
Also, to my my knowledge, Poser hasn't had a "core-rewrite" since Poser 4- so later versions are just add-ons and updates and fiddles with the original code, so not much underlying technology has changed. And it sometimes shows.
D|S is a new product written with at least half an eye on multi-core processors, bigger RAM capacity and an architecture that freely supports plug-ins and expandibility, so things that are missing now such as the face room, dynamic cloth support, dynamic hair, advanced lighting etc. will be developed as core additions or added and integrated by third-party developers. 

My overall view is that D|S is the way forward ultimately. And it's free, which is a huge bonus. That said, if you want the features now, then get a copy of P6 as recommended above. Don't get any of the "cut-down" versions; just get a full copy of P6 which- as stated- isn't much money at all now. And, you'll have a legitimate upgrade path to newer versions.

Still, since D|S is free, you might as well get it anyway.