Come on now... The 950XL is a big upgrade from the 1520.
More LTE-bands, Cat6 support, smaller, lighter, better screen, higher resolution, GG4, much faster SoC, better graphical performance, higher MicroSD support, more RAM, better cameras, more modern Bluetooth stack, updated gps stack, usb-c, iris-scanner (perfect during Winter), barometer, continuum, fast charging.
Literally everything you mentioned there is worth nothing to the average consumer.
More LTE-bands - from what I see (and you can't see much about that), they both support the following bands: 850Mhz, 900Mhz, 1800Mhz, 1900Mhz, 2100Mhz, 2600Mhz, HSDPA, LTE
And if you really need any other band, then IDK, you probably live on mars.
Cat6 - umm, what? Where can you plug in a cat6 cable in your phone? I'm guessing from the dock, but even then, that's not something that's made for widespread use, only some will find use in it.
Smaller, lighter - well yep, and I like my display bigger. 6'' > 5.7''. So, again, for me, not an upgrade.
Better screen - only more pixels, which is a downside if you ask me. Quite a big one. You don't need that many pixels, and it only drains the battery.
GG4 - well, yep, that's good.
Much faster SoC - not really. SD 800 vs 810 is not a big difference. Not to mention SD 800 is already really fast, so you're buying nothing.
Better graphical performance - same as above, I never found my 1520 lacking performance, it's a top end device, what can you do on your phone that requires strong graphics.
Higher MicroSD - I don't think so. I think both devices support any MicroSD card there is. And come on, who's gonna spend a fortune on a 200GB SD card?
More RAM - same as above, I've never found my 1520 lacking memory. Even if you multitask like no other the system manages it well and you won't fill up those 2 GBs.
Better cameras - I think they're using the same camera as on the ICON (930) / 1520. I've heard they've made some improvements, I've never heard anything else other than that. And once again, the 1520's camera is good enough (the only problem is the current app which outputs horrible pictures).
Improved Bluetooth - isn't that a software thing? I could be completely wrong here, so don't hold me on that one, but I don't think it's actually some huge improvement on the chip.
GPS - never heard anything about that, and I feel the same goes for GPS as for Bluetooth.
USB-C - yes it's nice, but no real advantage to it (other than it's reversible). It's even a problem for now, since there's not too many devices that support USB-C.
Iris scanner - goes under the gimicky feature. Fingerprint scanners, iris scanners.. all that stuff, it has almost no real world usage. Maybe in 20 years though.
Barometer - really?
Fast charging - yep, that's a good thing.
And as for Continuum, I can't lie, that's a big thing, but for me personally it's useless. It still isn't what it's supposed to be, and even then it's just going to be an improved 'project your phone'. I've never done something like that in my life to be honest. And I barely see why you would need such a thing. I kinda get what MS is trying to achieve here, but IMO out of the whole 3% Win10M market share, only like 10% - 15% are Continuum enabled devices, and out of those 10% - 15% I think 85% won't even use it. So you're basicly gonna have like 7 people in the world who are going to use it.
That's just my oppinion about it.
For you, it may be a decent upgrade, but for me, it's far far far from it, because most of the 'improvements' are just on paper. Not to mention my 1520 is gorgeous, and the 950XL is.. not really. We'll see about that Surface Phone, though.