If you attach a GPS to the camera, the camera usually updates it's clock automatically, and will still show the current time with or without daylight savings. However, if you want to geotag your pictures later, with a track from an independent GPS (which can be useful, as it saves camera battery, and the GPS may be used for other things) then using the Universal time means that the images and gps can be married properly.
I was able to geotag my South Africa images (from my D200s and a compact) from 2010 using the gps track I kept of our routes through Kruger National Park. It took a bit of fiddling around because back then I had set the cameras to GMT, but the gps showed local time. What I should have done was set the cameras to the correct time zone, then the geotagging in Lightroom would have put them in the right place at the first attempt. But back in 2010 I had no idea that geotagging would be possible.