Triac snubber: Where to put current limiting phototriac resistor?
Based on the simulation models, viewed from a distance, I would say at first that there is no difference.


A small thing appears because in the second case, the currents of the optocoupler became smaller.
Magnified, the difference is already visible.


In the first case, the current duration of the optocoupler is longer, the value of the current is higher. This is natural, because if we take a closer look, the optocoupler should discharge most of the capacitor 22n. The optocoupler thus conduct longer than the time required to turn on the triac. This is almost the time constant of C1 R2. So as usual we can choose between two bad ones. In the first case, the optocoupler will be protected against dV / dt peaks, but will heat up more strongly.
In the second case, the optocoupler average current will be much lower and its protection will be provided by a snubber located in the main circuit of the triac.
This is a little less protection. I would choose the second one (based on practice only, I can’t prove it’s better, it just used to be good).