Cover keyboard. Horrible touch typing response. And I know, I don't buy computers for keyboards either, but considering that typing is still a major avenue of data processing, it is important to have a decent keyboard. Apple makes the best keyboards on their laptops IMO.
As for the power, screen, and pen, I found the Note 10.1 to outrank the surface pro 3 in overall note-taking experience. AND it is MUCH CHEAPER. Have you ever used S Note? It is so well-made...I have yet to find use for all of its functions..I can take pictures of a chalkboard or whiteboard and insert them into my notes instantly, record a lecture by audio or video and insert instantly, highlight/annotate powerpoints, basically do whatever I want with the Note 10.1.
But then again, I was looking primarily for a LIGHT note-taking device which could deliver the tablet experience with movies. I use my macbook for all heavy paper writing etc.
The advantage of Surface Pro 3 is that it packs a windows operating system. But, as
@Digitalangel asked, surface Pro 3 CANNOT take the place of a computer without a decent keyboard...which it lacks. If you go detachable keyboard, then you're just increasing clunkiness and decreasing portability.
SO. Let me sum up my long-winded response. It depends on what you want to do with your device. For high portability, excellent note-taking, CHEAP PRICE, and the tablet experience , you cannot go wrong with Note 10.1.
The surface pro 3 offers integration with the windows OS which is decent, but its hybrid character makes it a poor laptop and to me at least, it is only moderately good at note taking. The cost is just not worth it. That is why I returned it.