HP has a series that operates the same way, I just thought they were a little more "chunky", which may not be all bad.
I checked all of these out at Best Buy today. Lenovo had a Yoga 710 that offered a lot of bang for the buck. Obviously it has a better keyboard than the Surface Pro 4, but it's also thicker and heavier than the Surface Pro 4 when you use it as a tablet. With the HP you are into 13+ inches screen size, which with the attached keyboard makes it almost unwieldy in tablet mode. And the optional keyboard for the iPad Pro is too flimsy. I think I'm leaning toward the Surface Pro 4 still.