For me, clipless pedals are safer than platform pedals with toe clips. I briefly used toe-clips when I first got into biking and it wasn't long before I went clipless. With clipless, you can quickly click out as you put your foot down. It is less natural, in my opinion, to pull your foot back and then move it left or right to put your foot on the ground.
Now, if you compared long-term cyclists on platform pedals (without toe clips) vs. cyclists who just started using clipless... that might be different. Most people fall at least once or twice when they first learn to use clipless. Another issue, is that most people use enclosed cycling shoes with clipless pedals. But on bikes with plain platform pedals, they may be wearing flip flops, heels, barefoot or all manner of shoes that may be less than safe...