As a current 1520 user, I haven't seen the benefit of jumping to a 950/XL. Sure it's going to load apps faster and take better pictures. But the 1520 already takes excellent pictures, plus apps load plenty fast. Heck, it even has 4k video recording. Windows Hello and Continuum aren't game changers (yet). And I don't feel like they will have any significant benefit in my day-to-day use. I don't play mobile games so that's a non-issue. And for the most part, the 950 is going to run the same version of Windows 10 as the 1520. Even though the 1520 is from 2013, I can't justify replacing it. I want a phone with increased capabilities instead of one that is just merely faster.
The Snapdragon 800 is old, I understand that. Yet I feel like it was a turning point for processors. The point were hardware started to outpace software. My phone is old but it's not bad. The 1520 is still really good. In fact, pretty much any 2013 flagship still holds up.