Cintiq 13HD, Surface Pro 4, or something else...

I've been using an Intuos Pro for years, and for my usual work (mostly layout in Photoshop and AI) it's fine, but I'm starting to use Painter more heavily and I find the disconnect between hand and image is more jarring so I'm biting the bullet and upgrading, but I'm struggling to narrow down my options. My first thought, naturally, was a Cintiq, but my budget only stretches to the 13HD. As it's pretty much an Intuos with a screen I figure that as an upgrade path it's the least painful, but as the Wacom name carries a premium I started hunting round for alternatives, of which there are a bewildering array.

Most of them (XP-Pen, Ugee, etc.) seem to be essentially the same product with a different badge, and the reviews I can find are not entirely helpful (mostly one-line Amazon reviews split evenly between "this is great" and "this is awful"), but the Huion KAMVAS GT-156HD looks like a decent bit of kit, and I did actually find an in depth review of it that seemed mostly positive; it's a similar kind of price to the Cintiq, but it has a larger screen and more buttons. (No tilt sensitivity, though.)

Further muddying the waters is that the Surface Pro 4 has just dropped in price bringing it pretty close to the same ballpark (at least for the base model), but for that you get a much higher resolution screen plus the benefit of it being a standalone device -- I don't very often take things on the road, but the fact that the Cintiq et al require mains power does make them slightly less convenient. I've had a quick play on one (although the only thing it had on to draw in was One Note) and the pen felt a little thin, and I'm not sure how it would perform under heavy use.

So, to my question: should I stick with what I know and go for the CIntiq, take a bit of a punt on the Huion, or throw caution to the wind and get a Surface?