I feel safer using my SPD shoes and pedals (same as OP's) because my feet seem to be less likely to slip off the pedals, particularly when riding over unexpected bumps while pedaling.

I've become so used to pedaling in circles that I have to deliberately pedal more carefully when I ride the platform side in sneakers so as to not slip a foot off. So perhaps another way to look at it is that my SPD use made my platform cycling less safe....but my preference is always to ride clipless.