Desktop-Name, Desktop-Power. Although we do not appreciate the name of the mobile GTX 980 because it can be easily confused, NVIDIA's new gaming flagship performs impressively. Our test covers the performance in Full HD and 4K resolution.
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-980-Notebook-Review.153013.0.html
According to your database, the 970M SLI set-up does indeed have problems; it can have fewer FPS than a 980M on Watch Dogs while having higher FPS on the Witcher Wild Hunt.
But with regards to emissions and energy requirements you state that a single 980 is better than a 970M SLI, however your review on the Schenker W724 shows that emissions weren't too bad. Meanwhile, the power requirements of the 970M SLI is 162 watts, so it seems to beat the 980 desktop at 180-200 watts.