not trying to start a debate but confused by this comment? More powerful? How is UGUI more powerful??? I have used it, it is light years behide NGUI. , is it better than NGUI not even close. Its good for those that do not have anything. I would rather use 2D tool kits UI, than UGUI. I use 2D tool kit for many other things, but when Unity came out with 2D , everyone freaked out and said 2d tool kit would become useless. Well, I have used both and I still prefer 2d tool kit for animations. Not trying to bash UGUI, it will be great for those that have nothing.
Also, UGUI, and NGUI can be used together... One reason NGUI can be weaker, that it can be scary for some since it has a bit of a learning curve. I still learn new things with it every day, but I will not make the switch from NGUI to UGUI ... I may use together but that's it... Heck I use NGUI and 2d a lot together, since I like some things better in either Asset.
If they stopped NGUI today, I would still use it.