Technikaffee.de site made a comparison of small barebone PCs for OpenELEC / XBMC use. It was interesting to see, that the Haswell i3 NUC is actually consuming less than the Bay Trail NUC when playing a 1080p video in OpenELEC.
The article is in German, but the power consumption figures they measured stand at:
DN2820FYKH (Bay Trail)
- OpenELEC Menu, 8 watts
- OpenELEC 1080p, 12 watts
D34010WYK (Core i3)
- OpenELEC Menu, 7 watts
- OpenELEC 1080p, 9 watts
The difference is quite significant. Both processors are made with 22 nm technology and the maximum TDP for the i3 is 15 watts and for the Bay Trail model it is 7.5 watts. Not sure how the exact measurements were made by the guys over there, but at least we can probably conclude that by choosing the i3 model you are not actually getting a model that will consume more electricity in normal use despite the 100% larger TDP compared to the Bay Trail model.