When it comes to productivity, no tablet is as good as the Surface Pro 3. Of course, that tablet also comes at a very high price. While the price is justified for a laptop or desktop replacement, it wouldn't make financial sense to purchase it as a companion to an existing Windows computer. Sure, you could go with a small-screen Windows tablet, but currently, app selection isn't too great (it is getting better though). In the meantime, an Apple or Android tablet would serve as a better companion.