As usual, Irulan has very wise advice.
I tried out my husband's SPD that are built into flat pedals, Shimano M424, a few times. I even tried riding downhill unclipped on the flat part of the pedals because I know that I cannot unclip fast enough if I fall.
My "frozen with fear" body on the downhill switchbacks was not worth the 10% uphill improvement being clipped in.
Back to my beautiful Campon flat pedals I go.
2014 Liv Lust
2013 Specialized Fate Expert with carbon wheelset (sold)
2012 Specialized Amira Elite
2010 Santa Cruz Juliana with R kit and Crampon pedals (sold)
2011 Specialized Ariel Sport,suspension post,Serfas Rx Women's Microfiber saddle (sold)