Well...if you want an actual phone the iPhone would be the best option. It's going to depend on your use & preferences. You'll have to figure that out on your own
I agree with Nikki, but I have a question for you. If you simply wanted to know the benefits of the iPhone over the iPad as the title indicates, why the need to state that you have a Samsung smartphone, a Toshiba Ultrabook and an Asus E-Pad? How is mentioning those items rationalizing the benefits of an iPhone over an iPad? It's early and I haven't had my coffee yet so maybe I'm missing the obvious...