Idol 4s would have been my choice because of the snapdragon 820. The camera seems good enough. Lumia 950xl has one of the best cameras sure but does that really matter that much? We aren't professionals. You look at an iphone 6s photo it looks good, you look at a samsung photo it looks good. You only really know which camera is better if you compare side by side.
The specs that sites are showing don't seem to be listing NFC (though the android version has it so it just may be windows sites leaving it out?). And seems MS is updating their wallet app with more banks. Granted here in Canada our debit cards support tap to pay but they are limited to 100 dollars due to no authentication occurring of any kind. So you lose your card anyone can just tap to pay for things before you realize.
If tap to pay is something you may want in the future then I would investigate further to see if NFC really is missing. Otherwise go with the alcatel. Honestly the 950xl is great but it is a battery hog and the 810 chip can only do so much. It was plagued by issues of heat and throttling. Ms has done a marvelous job with it but no phone can get it tamed perfectly.
The question is if alcatel will be supporting the device...... Who knows when we will see a firmware update from them...
I really would not mind picking up the Idol as an upgrade from my 640 but.... my question above has me pondering.
If the device is great out of the box with no issues that would require firmware update then go for it. Not getting firmware updates isn't a big deal if the firmware is done well from the start. HP had some troubles but they are new to the phone business, Alcatel isn't.