I consider this to be old style:
And this to be new style:
I like the new style better, as the clips that have two thingies for the strap to pass through at the top of the foot makes it more comfortable to me. I notice plastic tend to be new style and steel tend to be old style.
Note that the picture of the new style also shows the strap used properly. The end is not tucked into the loop. This makes adjustment easiest.
I agree with @
Prowler that leather straps are much better than nylon straps. Nylon straps are too floppy and can get snagged. They also don't last because abrasion wears them quickly.
So if functionality is your primary concern, sacrifice the good looks of steel toe clips. Get new style plastic toe clips and leather straps.