Using flat platforms and wide straps like Power Grips gives one the premium option of adjusting one's feet on the pedal's nice big flat surface. Yes, it's good to have the feet secured to the pedal. However, with any type of cleatz your feet are locked into one position, right? Also, while having the skill to pedal in "circles" it's been proven there is very little if any real advantageous force being actually applied on the upstroke side. But, standing up on an uphill climb does seem to be better if the feet are tied to the pedals.
Here is a great report for your open-minded consideration:
http://www.bikejames.com/strength/th...h-flat-pedals/
http://www.bikejames.com/wp-content/...withLinks2.pdf
By the way I use C R O C K S on 186 mile brevets in one day and I have no issues about soft footgear. Because I did one brevet with the left foot using SPDs and the right using a Crock. I carried the other SPD sandal along, just in case. Result, my right foot felt sooo bad with the Crock. Not!
This year I have worn Crocks for 4,202 miles... so far and without any desires to go back to stiff soles clipped in.
Just to be open minded I will flip the two-sided pedals over (now that I've fully adjusted to flat pedals) and wear my old spd sandals for a while and see if they feel a lot better than the soft ones on a 300k brevet.