The practical half of my brain says I should take the little Lumix LX100. It's a great little camera, easy to cart around and I can just toss it in my backpack when we go walkabout.
Then I spend a little time online, looking at the places we're about to visit - Singapore, Bellagio, Klosters, Bad Gastein, Graz and Venice. Just now, I booked a table at Singapore's 'Supertree' restaurant, Gardens by the Bay, and those gardens are just brain-bogglingly spectacular at night. Photo opportunities? Only a few hundred.
Mist over Lake Como, Alpine flower meadows around Davos, roaring waterfalls and majestic peaks in Austria, the dimly-lit interior of the Styrian Armoury in Graz and swifts doing evening circuits around St Mark's campanile in Venice. Hmmmm, the Canon 5D3 with 24-105mm would capture those so much better. So long as my neck and knees hold out.
I'm less inclined to turn every stop into a photoshoot when I have the LX100 with me, but from time to time, I find myself frowning as I process a really nice shot taken with it, with blown highlights or impenetrable blackness where the 5D3 would reveal detail.
I have packed and repacked several times. LX100, then 5D, then LX100, then 5D. Currently, the LX100 is in my carry-on.
But there is time for me to change my mind ...