Although this article is older it is relevant; I bought a used Dell XPS13 9350 and it only had a 128GB SSD. I went on Ebay and bought a Crucial 1TB SSD and just finished installing it following your instructions and using the recommended software. I have to say, everything went flawless; thank you for this article, the very easy to follow instructions and pics. This was a fun project!  :D

One thing your article did not mention - if you're using BitLocker (as most people should since ATA password is pretty easily bypassed) - you likely want to use hardware crypto from latest SED SSDs from Samsung or Crucial eDrive/E1667 compatible.

BUT - you *cannot* restore Windows as during install (on blank SED) it generates and sets the crypto password even if you don't engage BitLocker. So you need to clean-install to engage SSD hardware AES crypto.

I've used this since XPS13 9333 with Crucial M550, 9343 and 9350 with Samsung EVO 850 and BitLocker hardware with no issues. There is no performance delta as the SED SSDs always encrypt/decrypt.

Unfortunately I don't know of any NVMe eDrive supporting SEDs; the Lenovo X1 SM951 NVMe is OPAL2 enabled but not eDrive/E1667 so you need something else not BitLocker to use its hardware crypto. Pretty silly if you ask me...

As for the 950 Pro much vaunted OPAL2/eDrive firmware is still missing-in-action (MIA) after being promised in November 2015!!! I think it's fair to conclude it will never appear...

Guys check out the NUC AnandTech article "Choosing the Right SSD for a Skylake-U System".

The reason for the XPS lower-performance SSD bandwidth is the same as the NUC6 i.e. the OPI link is set to GT2 not GT4 thus 2GB/s is the max bandwidth. Intel has finally fixed it in the latest BIOS (ME firmware really) but it is a pain to apply. This is done to save power which on an ultrabook it makes sense.

You can dump the ME firmware from XPS and look at the settings. But you won't be able to flash a modified one easily the ranges are protected.

If you have a BIOS programmer and you're happy to try messing with the BIOS you can set it to GT4... Good luck!

NVMe drives have serious issues in power consumption. The best should be the 950Pro but it still uses way more power than a traditional AHCI SSD. You should include a test on battery life, too.