Not sure about architecture itself, x86 seems to have more hardware to support a broader intruction set and the Operating System itself (say Windows) seem to have way more overhead than ARM stuff, mostly due backwards compatibility I guess. The Switch may run closer to the "metal" than a similar x86 device.

Power efficiency seems higher on ARM Soc's but I have a old Asus Android tablet wich is powered by a [url=Ihttps://www.gsmarena.com/asus_transformer_pad_tf103c-6409.php]Intel Atom SoC [/url] and at the time was not that bad in battery life and performance compared to similar price tablets.