Design suggestions for a comparator circuit

I made a circuit which will convert incoming pulse train to shaper cleaner pulse train. So I used a Schmitt trigger circuitry.
Basically the circuit will be supplied by 12VDC. And the input pulses can be between 4V to 11V amplitudes. Phase shift is not important, since the application is to count the pulses for a long period.
Following is the circuit diagram:



As you see above, R_opt is on or off by a switch. It is off for input pulses for 5V and on for input pulses at 11V for better results.
ZD1 and ZD2 is for surge protection. C2 is for filtering HF noise. And the circuit has quite large amount of hysteresis. LED blinks for each pulse.

But for a better noise immunity for the power supply I have seen such topologies as below with R_x:

Topology 1:




Topology 2:



Do you think I need Topology 1 or Topology 2 to eliminate a possible power supply noise or just my first diagram would be fine without any R_x?

I would be glad to have your suggestions or critics about this circuit.

Depends on your noise. If you're really concerned about noise you should derive the voltage for your divider on the (+) input from a zener or voltage reference, not right from the supply rail. Topology 2 would be a very bad choice, since the reference voltage will vary with the comparator current draw.

And I don't think you need Zd3. Just size your resistor to limit the LED current.