The pros and cons post by runix is a very good summary.
I have a 5.5 Kg 17.3" laptop and I can tell you for carrying around it's quite a hassle. It's heavy and cumbersome and takes a lot of space in public transportation. I even had some back pains the first weeks due to the weight.
That said, for gaming I like it very much. Came to it from a 15.6" and the bigger screen was noticeably better, plus the better thermals and capacity for larger components (GTX 1080, though I think there are some 15.6" with 1080s now).
I didn't quite understand if you bought it already but if you already have a 1070 maybe you can consider waiting for the next generation of cards then jump straight to a 1180? It will be more bang for the buck specially since you already have a very powerful rig.