I would love the 950 for the better ppi and pocketability. Plus the XL has a strange button layout that I feel I wouldn't like. Also, that ring around the camera is sexy!
Either would be a huge, huge leap from my current L520, but if I were to choose, it would be the 950XL, because why not? hahaha. I've been taught to always reach for the stars so no even though you fail, you'll land on the clouds (the 950, hahaha).
Even though the Lumia 950 XL is a wonderful device, I would prefer the Lumia 950 as it is the more compact option and specs are very similar. Both devices pack top-notch hardware, an amazing camera, liquid cooling, great processors and I can't wait to play around with Continuum! People will really be amazed by what these devices can do!
While I would love an 950 XL for myself, my wife is hopefully out of hospital today with six weeks of absolutely doing nothing (or see will end up back in hospital) and 6 months full recovery. She has never had a flagship phone (makes do with a budget or mid-range). The XL with it's large screen and battery life would be wonderful for her.