Can I just say the Internet Explorer is much more efficient? I hated the Wii and 3DS browsers because they were inconvenient for browsing, but on the Wii U it's much more comfortable.
Aside from that
The gamepad is simply amazing. I surprisingly found it more comfortable to use than I thought. Playing straight on the Gamepad is a great thing because there are countless times where the TV is inaccessible and having the Gamepad to interact with always comes in handy. Having a touch screen controller also adds a whole new layer of ideas to use for games. Unlike the PS4 and Xbone I actually felt like the Wii U had a lot of change entering the new generation. Nintendo thinks outside the box and that's good, I feel like I'm going to truly enter a new experience when I buy a Wii U.
I think reducing to 5, more general reasons is a good idea. You'll have more to talk about with each topic.