I realize the OP has already taken the plunge and seems happy enough with his decision, but I still wanted to chime in.
IMO, and I'll likely be chastised for this, you'd be a fool for choosing either of the two at this point. If you really, really, really love Windows 10 Mobile, sure, go ahead, but don't base your decision on previous experience with Windows Phone 8.1 as there are so many things still missing, not working properly or just plain different between the two.
Also, neither handset it a real flagship. The 950XL (which I use - my wife has a 950) runs too hot, eats battery charge like there's no tomorrow (and this is actually my third 950XL so not just a bad device), the screen doesn't "pop" like I still think my good old 1520 does, is too small for my liking (but I realize this is highly objective), doesn't seem to perform as well as you'd expect it to (or rather, certain games and apps aren't optimized for Windows 10 Mobile). No fingerprint reader (sure it has "iris" recognition, but c'mon that sucks and takes ages to unlock the phone compared to a fingerprint reader - I've got others with fingerprint and it almost feels like they unlock before you even touch the sensor, Iris takes a second at least). The list goes on.
Seriously, this past Sunday I hardly used my phone at all. Got up around 730 am, had a quick breakfast and got in the car with my son to go to his swimming class. That's a 20 minute drive, during which I listened to Windows Weekly using the standard podcast app (audio was pre-downloaded, no streaming involved). Was at the pool for a good 90 minutes, quickly checked phone for messages after getting out and put it back in my pocket while we went to get lunch. Rather than staring at my phone during lunch I talked to my son and we got back in the car as we were going to visit his grandma which is almost a 2hr drive, listened to an Audible audiobook for around half of that (again, this was pre-downloaded, no streaming involved). Did some more messaging (facebook and skype), updated my Facebook status once, took a couple photos during the day and spent perhaps 15 minutes using Cortana/Edge looking for some information. During the drive home I was on the phone, talking, for 24 minutes and 11 seconds. At 640pm my phone is completely discharged and switches off. And this was a good day - generally I use my phone a lot more than this and I have to recharge it around 4-5 pm. Then with some candy crush gaming after dinner and general usage while watching TV the phone is again ready to be recharged by the time I go to bed. That's not even somewhat acceptable in my book. My good old 1520 was (and still is - after a Win10M upgrade) soo much better in terms of battery life.
I feel good that I purchased these handsets simply because "every little helps" in terms of the platform as a whole, but had I known then what I know now I'd probably have waited it out a little longer and got a HP Elite Pro 3 or the elusive Surface Phone. Or, if Windows 10 Mobile still didn't feel ready probably jumped ship to Apple. I don't really want to, but with everything Microsoft is doing "wrong" it's heading in that direction - and that's spoken as a true "fan" who owns several Surfaces, mini-tablets, windows phones, xboxes and god knows what.
Sorry for the long ranting post, but I'm beginning to feel a little fed up. Had Samsung, HTC or Apple sold a product as "good" as the 950XL there would have been a public outcry. When Microsoft does, it's somehow okay because the product is only aimed at the hardcore windows phone fan? Really?