Welcome to Android Central! You may want to consider devices that aren't quite as high end and expensive, if that's mostly what you're going to use it for. The Tab S is Samsung's flagship, and the Surface Pro 2 is kind of like a laptop crammed into a tablet. If you were going to be doing lots of gaming or processor-intensive activities like video editing, then a high end device might make sense.
If your choice remains between the Tab S and the Surface Pro 2, I'd go with the Tab S. It's more portable (the Surfaces tend to be a little heavy compared to conventional tablets), and has a bigger mobile app ecosystem.