Deltas are dinosaurs. The original LOOK pedal and cleat.

I ride Delta cleats and Forte LOOK compatible copies on my good bike, using the black (no-float) cleats. They work just fine. I will have to upgrade to KEO (LOOK's upgrade of the Delta system) or SPD-SL (Shimano's entry into the LOOK-style pedal or Speedplay Zero (which are completely different) when my stash of pedals and cleats run out to keep the no-float (and my knees).

I have never used the Delta red (float) cleats and when I have used SPDs I have the toe-in cranked to the max so there really isn't float in the normal sense, hence I cannot answer for you the difference in the two pedals. (No-float is no-float and the pedal makes very little difference. My toeclips and traditional cleats ride just like my black Deltas.)

Both systems (Delta and SPD) are well proven. They have nothing in common beyond working really well.

Ben