The first contains a bundled ADT version of Eclipse.
This is simply a packaging convenience. You are welcome to obtain Eclipse separately and add Android tooling to it.
Android Studio, the second IDE, is based on IntelliJ.
At the present time, this is an early-access preview. IMHO, it is not suited for someone who does not have experience in Android application development.
Apart from these differences I can't get if there is anything that I can do with only one of them
At the present time, Android Studio is an early-access preview, meaning that there are lots of things that it does not have integrated in. Now, by this time next year, and hopefully far sooner, Android Studio will have equivalent or superior integration than does Eclipse with the ADT plugin.
and what's the point of having two distinct official IDEs.
There are an infinite number of "official" tools. You are welcome to use a plain text editor and tools outside of any IDE, for example.
You are welcome to watch the Google I|O 2013 video on developer tools, where they describe a bit of the rationale behind the development of Android Studio.