I think it's more a matter of customizability and extra options.
I do think the iPhone and Android phones are very similar, which is why it was so odd to me that one would be intuitive to some but not to others. I think it's because Android apps generally have so many extra nested options - which is great for someone who wants complete control over their device and its apps, but not for someone who finds that sort of thing intimidating.
With the PB, you really see the concept of the "long press" to bring up more options. Select a book, do a long press, and there suddenly you have a menu letting you decide how to open your book - FBReader? AdobeViewer? PDFViewer? FBReader180, your custom app? CoolReader?
With Sony, you don't seem to have those options - you press a book and it's open. The end.
For someone like me, having different reader options is a bonus; for someone who finds that sort of thing tedious to use, remember, and manage, it's a chore. (Or overwhelming!)
So while I don't think the PB / Android interfaces are especially similar, I think the ability to do whatever you want with your device is (as opposed to "one right way" to do things).