From my experience VRAM is important especially if you ever plan to use vegetation which without a proxy system will eat your VRAM fast, so my advice is to go for the most you can afford.
Both VR Headsets are great, but implementing the positioning system of the HTC is more complex than the one of the Oculus.
So therefor you can use the HTC Vive currently only with flymode in Enscape.
For now the Oculus Rift would be my choice.
Jonathan Knoefel will the issues with flymode and the HTC VIVE be resolved anytime soon?
Or wait a little longer and get one with a 1080ti in it... It's reportedly ~35% faster than a standard 1080 and only costs $100 more (although I think they may have dropped the price of the 1080 now). http://www.tweaktown.com/news/…ps-coming-soon/index.html
Definitely the 1080ti is current king, I have 2 in my machine and wished Enscape supported multi gpu.
But wait! - Nvidia just announced the new Titan XP today, meaning the 1080ti's reign has been short lived. It costs twice as much though and is unlikely to be offered in a laptop.
Yes tnx, Jonathan and others, yesterday I ordered the Alienware with 1070, cause the 1080 and Ti (later) will cost me a bit too much..... I guess I can get along for a time for now, and: next week we are going to order a floating license!! YEAH 
So the next step will be a choice between the Oculus or the Vive -> I need:
- roomscale experience, with moving in a square 4x4m
- gliding witch controllers,
- teleporting
Good choice as well!
At the moment I would recommend you the Oculus Rift cause we haven't implemented the positioning system of the HTC Vive completely so far as mentioned above.
You'll get roomscale experience: https://www.oculus.com/blog/oc…ting-up-a-killer-vr-room/
And you can fly (glide) and teleport with the Xbox or the Oculus touch controllers and can walk around as well.
but if you can wait longer and the 1080 Ti gets available in Laptops, maybe in 2 months from now, I would hit that one.