I like both, I really think the new one has a nice colour scheme and layout (not nicer than Taleworlds, but very good in its own right). But I think Taleworlds has a larger width of posting space (NW seems to be more confined to the centre of the screen), and is a bit easier to read. Plus of course the whole M&B community is here. I will visit both, and I hope new Warband/NW players will visit both as well. It would be a shame for them to miss out on all the Warband mods and wealth of knowledge on this forum (modding know how, facets of singleplayer which aren't in the manual, guides on improving multiplayer skills etc.).
I expect the official NW forum will be a bit calmer and more welcoming to new players, and the fact that it is dedicated purely to the DLC should mean it provides a more consistently relevant source of information and discussion for the community. Whereas here, being a sub board there are often references to other mods and native issues which are of interest on the Taleworlds forum but might be superfluous information to wade through for a new player wanting concise discussion or information on NW.