I'll be as honest as I can in my reply. I own 2 x 950xl. I have a black and a white one.
The 930, which I also have, is a great device, and still, in my opinion, a great phone, if you forgive the terrible battery life.
Back to the 950xl. These are very well spec'd devices, and they perform admirably on the TH2 software. My only real gripe is that they look bland and are very plasticy. On the threshold OS, 10586.XX they are very smooth and pretty snappy. They do warm up somewhat, and you wonder if the so called 'liquid cooling' is a gimmick, but I guess it does draw it away from the CPU. In hand, they do take some getting used to as they, to me, are quite slippery. A case or a Mozo back soon sorts that out though. I love mine and they are used in a business environment with battery consumption being acceptable. I've had no real issues with crashes, lock up or plain unresponsiveness. Even Continuum works great on mine.
The BIGGEST issue with the 950xl, isn't the phones problem. It's the software. The device is so underused. It's like its out for a Sunday stroll! The new redstone OS, due end of July(ish) makes much better use off the device. On the preview software, it's like lightening, and thats where it will come to life.
As for recommendations, I couldn't advise either way. The decision would have to be yours. All OS's have there own quirks, failings and positives. I left android for windows, and I'm not going back. One little piece of advice, learnt from personal experience, I wouldn't buy a top end android phone again. The update cycle for some of them stop pretty abruptly after 12 - 18 months, and the way in which anti tamper measures are being introduced, rooting and custom rom choices are reducing.
Best of luck, and whatever you decide, I hope you enjoy it.