Honda Civic

1997 honda civic 100040 mileages.
my check engine light was on. The diagnostic trouble code is P0420 Catalyst System Efficiency Below Threshold (Bank 1), one repair technician told me I should replace a new catalyst converter, but another one told me to replace the new O2 sensors, what should I do? Thanks.
August 13, 2006.

Have someone check the 02 sensor wave patterns on a scope or for being out of spec. In particular the front one. Converter is probably fine, but further testing should be done. If testing was done, not just a conversation, then you'll need to have faith in one of the techs. That code points to bank1-02 sensor. The front sensor evalutes gases before entering the converter and the rear one evaluates it after the converter