I'll vote for platforms being safer. One ancedote I detailed here:
http://www.bikeforums.net/advocacy-s...-thursday.html
I would definitely have crashed if I'd been clipped in - or worse - possibly hit by a car.
I've been riding with toeclips since 1979, and clipless since 1991, so I've had plenty of experience being clipped in.
Personally, I've had some ugly crashes while clipped in. Sure, your pedals will probably release AFTER you hit the pavement. But if you are in a bailout situation, I think you are far safer not being attached to your bike.
The one situation where you really can't get out of your pedals is when you are heading over your handlebars.
I've experienced this a couple of times, unfortunately, and if I could have gotten unclipped, I would have. Instead, I went over the handlebars and dragged my bike with me. Hard to tuck and roll in that situation. Luckily, the first time it happened, I was able to break my fall with my face - thank god my bike was safely attached to my feet, out of harm's way!
I only got a pair of platforms about a year ago, for winter riding in Sorel boots. I won't ride clipped in in the winter. If you can get your foot out of your SPDs and onto the ground as fast as you can with a platform - good for you. I can't.
That said, I still use my clipless in the summer. I like SPDs, they are comfy, great for maximum efficiency. But they really don't help if (I'm) in a crash.