With my lose straps, I can remove my feet instantaneously, even during a fall. Ive removed my feet during a fall on ice, and riding off-road when I slid down a deep 4x4 tyre rut. Can you get your feet out of clipless pedals in the moment between losing control of your bike and hitting the ground?
i have spent lots of time riding with both "clips and straps" and clipless pedals and never had a problem with either.
i can unclip more quickly from my clipless pedals than i can get my feet out of clips/straps.
as far as clipless pedals and an emergency/fall: yes, MOST of the time i can unclip if i anticipate a fall, but there are those occasions where your are suddenly on the ground - i these cases my pedals have always unclipped themselves (most of my experience here is with Speedplay Frogs although i had traditional Ritchey Shimano-type SPDs for 1 yr) either by the force alone or the pedal cleats twisted in the shoe and unclipped. in other words i have never had a fall where i either a) was not able to unclip myself or b) did not come unclipped in the course of the fall, so i have never had a major fall and stayed clipped into the pedals. i suppose it's possible with some of the pedals to set them up SO tight that they wouldn't release, but there is no need to set them so tight.