I went into London before sunrise, looking for good photos.
(Which sounds impressive, but it was December 29th, and sunrise was about 8am!)
Knowing that the sun rises behind Tower Bridge, I smelled an easy photo opportunity. But woe is me - I can't decide which one I like better!
The landscape version (above) has more focus on Tower Bridge itself, partly because of the strong shadows in the water and the tighter focus which makes it dominate the picture. But the portrait version (below) has more dappled water, a more interesting shoreline and that wonderful sky comes into focus.
I suppose it depends on how you want to look at the picture. If it's a sunrise, you want the portrait version - it's about the whole scene. But if you want a picture of Tower Bridge, then the landscape version is your kind of thing.
The only real option is to give the world both. At once. And then hold a gun to your head and make you choose.
Stay right there looking at these, whilst I go fetch something....