For me, one thing a tablet has a decisive advantage over a bog standard laptop is (as you've already noted) the reading of PDFs, and also other ebooks, comics and similar stuff in portrait mode. Sure you can do that on a laptop too if you don't mind holding it clumsily and awkwardly in portrait orientation.

I recently got an Asus TX201 Trio - it's a 3-in-1 thing - the "keyboard" is a full x86 system which you can use independently by connecting to an hdmi/displayport monitor, the "screen" is an intel-based android tablet, you can connect the screen to the keyboard to use it as a laptop. When in laptop mode you use a dedicated button to switch display between "PC" and android. During the day I use it for work in laptop mode, at night I detach the screen and use it as a tablet for reading comics or watching videos to unwind.

As others have said for serious work you definitely don't want to be using a "tablet" OS. Eg on my desktop firefox I have 2 windows with a combined total of well over 100 tabs opened - try doing that on a tablet.