For me personally, the main issue with the 50/34 combination is the 50t is probably too tall unless only riding on flat terrain and the 34t is too low to be useful in any situation other than climbing. If a person needs a 34, it would seem better to go with a triple.

A number of years ago I had set up my wife's bike with a 46/36 but the 36t was a little too low. She now rides a triple with a 46/39/30 and the 39 works well for most of her riding and the 30t is always there when needed.

I've gone from a 52/42 setup I have had for years to a 48/38 and it seems to be a good setup. The bike still has a Sachs 7 speed freewheel with a 12t so I lose nothing over a 52/13 or 52/14 for those very few times I actually use a 12t. So far I've made up any difference between a 34t and 38t on the low side of the freewheel; running a 32t. I am planning to go 8 speed soon and will run a 12-34 cassette that I think will serve me well in every situation. I have been able to run up to a 30t with a DA RD, but I am now running older XTR RD and the setup is quite enjoyable.

John