I will give some short opinions here. First off, I purchased an AT&T Lumia 950 at launch but returned it and purchased a 950XL since I felt it to be the better device. I sat on the Idol 4S but do have the BlackBerry DTEK60, based on the same reference design but running Android. My daily driver for now is the HP Elite x3.
Lumia 950/950 XL: Great camera for still and videos, removable battery if you are a power user or plan to keep the phone for ages, swappable backs if you want to change looks, the most 'supported' when it comes to features like Lumia Extras, NFC payments, etc. It does feel a bit cheap and creaky in the hand, but at least it offers the most case options if you do want to change up the look or protect the device.
HP Elite x3: Massive for a smartphone, I like having dual SIMs that still function (the chip on the 950/XL doesn't support 3G on SIM2, making it unusable for AT&T customers as the 2G GSM/GPRS/EDGE network has been shut down, I know this is the case in some but not all regions). The x3 has been my daily driver since March. It has held up pretty well and rarely been in a case. The chrome-look plastic is a little cheesy but has held up better than real metal, with a few minor scratches but nothing too crazy. The camera is not great, but having fingerprint and iris scanning available for Windows Hello is good, and the screen is beautiful. If your phones take a beating regularly, I would say this is probably our best bet. The Continuum dock is -- like on the 950XL -- a bit of a gimmick but I do find myself connecting via the Miracast "Connect" app on desk top to use some of the functions of the phone while on my PC.
Alcatel Idol 4S Windows: I can't speak to the future of support on the Windows 10 version of this phone, but the glass back and cold-to-the-touch metal do give the Idol 4S far and away the most premium feel of the current W10 flagships. I have the BlackBerry Android variant of the 4S and the camera does OK, but from what I hear it is much slower on the Windows 10 version. The 2K display is scaled back to full HD as well versus the BB version of this device and W10M competition, but still -- this phone looks great in person. If you want to feel like you have a premium piece of kit in your hand, this is the Windows device to get. And, depending where you live, it is great value for money -- especially here in the US.