The reason is quite simple, index options are used by more professional traders as hedgin strategies, equities options by small speculators, I try o be a contrarian to the small speculator, or Mosis, not the manipulators of the market and that is why I only look at the equity P/C ratio. ofcourse, I have "calibrated' my system to the equity P/C as a result. I tried to find correlations with very high put buying in equities (like today) and market top (assuming the "big bouz know more) but have found no correlation to the market. However, I found pretty good correlations between the equity P/C ratio and market future behavior.
Zeev