It doesn’t really make sense to ignore energy consumption in a supposedly portable device. That’s like saying that a ship is more efficient way of transport, if you ignore that it can’t go over land.
Portable doesn't necessarily mean it needs to last as long as it takes you to hike accross a continent.
I use a laptop because I can move it from one room to another without shutting it down. While it would be nice to not have to plug it more than once a day, I'm fine with a 4-5hours autonomy.
But having more battery life definitely do not beat having functionalities such as external monitor, working internal webcam and sound.
