Larger pixels are not more sensitive to light - the A7s's sensitivity ("quantum efficiency") is about equal to that of the D800/A7 - this is why midtone noise on the A7s is the same as the D800/A7r when compared on a per-area basis (via downsampling). What larger pixels do provide, at least with current technology limits, is better Higher ISO dynamic range, which is due to the total lower cumulative read noise from fewer pixels having to be read over the same area vs a higher MP sensor. This translates to lower noise in the shadows. This larger pixel advantage turns into a disadvantage at base ISO because of the read noise penalty from holding a larger charge (full-well capacity). You can read more details at my dpreview thread here: http://***URL removed***/forums/post/53860364