NGUI has grander scope than uGUI, in part due to legacy support (creation of atlases and bitmap fonts being two such examples). uGUI is a lean version of NGUI that does some things natively in C++, gaining performance but sacrificing flexibility. uGUI isn't "from the same developer" though. I am just one of them. It's true that I started it, and it's true that it derived from NGUI's codebase, but now there are several devs working on it, and I am moving to the shadows myself (I'm really itching to get back to game dev).
I will keep supporting NGUI while people are using it, and I will keep adding things to it to make it better. But that's about all I can say on the matter right now.
