Definitely the 950XL. Love the large screen. The camera is amazing. I think it blows the Iphone camera away. Removable battery and expandable memory. Only thing it is missing is a few apps and I can definitely get without those apps.
Difficult choice, but I'd likely pick the 950. I have an XL on the way, and having the other for development and comparison purposes wouldn't be a bad thing.
I'd like the Lumia 950XL because of the larger display, faster processor for processing photos and video, and because the design is more aesthetically pleasing to me!
I would go with the Lumia 950XL, because the overall size is not much different between 950 and 950XL. However, 950XL will offer better hardware than the 950.
I'd take the 950 XL because I've always been so anti-phablet, but my curiosity is getting the best of me. The specs are always better on the larger phones, so if I can manage using one, it would be a better setup.