Even Hagoromo feared the occular powers of her mother, therefore, I think it's a little bit better than a Rinnegan. However, the strength of a Dōjutsu depends always on the user.
I also think Madara will try to take it and probably succeed as well, maybe Sakura will destroy Obito's Rinnegan which will leave Madara with one option. It's no coincidence IMO that his left eye is the one that awakened.