I've crashed with clipless, toe clips strapped in and open flat pedals. No differences in injuries -- too many other variables determine the likelihood and severity of injury, not foot retention or lack of it.
Get the pedals or foot retention type that suits you best while riding and ordinary stopping -- traffic lights, etc. I wouldn't buy based on a hypothetical crash.
I'm accustomed to old school Look Delta but those are terrible for walking, and aren't great for setting a foot down at a traffic light or whenever necessary to stop and go. SPD-SL are very similar but add grippy rubber pads that hold a bit better on sandy pavement and are a little less awful for walking.
Most of my friends use mountain bike type SPD pedals and walkable shoes, or comparable stuff by other makers. They're more sensible than I am.
One friend prefers Speedplay, but whenever we ride and need to stop or walk around, it seems like he's always fighting to clip in again because pebbles jam the works -- especially in damp weather when sandy pebbles stick to everything. Heck, I get that problem occasionally with Look Delta and SPD-SL, but not nearly as often as he does.