100mW is not a lot to use during such a contest and indeed I worked one ON using the 100mW and he told me he was using 1kW! There was a slight difference in the reports with 40dB power difference......
What was interesting was the difference in ability of some stations to hear me and others to not even notice that anyone was calling them. How much was down to receiver blocking at their end and how much to shear QRM will never be known.
An interesting evening.