The 1020 has an AMOLED screen, meaning the above. Darkness highly recommended.
More bright colors means higher power consumption.
But if the battery holds up with it like that and you like the primary white look, feel free. I had a friend who used a Lumia 900 with the white theme. not ideal, but that didn't seem to stop her.
White theme will impact your battery..since more pixels are being in a constant "on" state, the draw will be greater.. By how much depends on the screen tech in use on your device. AMOLED yup.. Prepare to take a hit. LCD, bit as much..
Ok, I am averageing 30 percent worse battery life with the light theme compared to the Dark theme. Back on dark. I can get through the day in dark and have over 60 percent battery left, I was down to 20 percent on light.