You could flip a coin, yes or no, you stand 50% chance of getting it right(or wrong) for the 30+ days that you are walking, thats how I feel when it comes to the the weather.
Unless I was walking the Frances in deep winter, late November to early March I would give them a miss, you will get dirty wet boots outside of that period but not hopefully too much. If you are not really sure after all the different advice, pack them, if they are lightweight you wont really notice them. I did not take any in November 2010 and did not regret it, if I had walked the same period last year, from all the blogs I read, I would have regretted it.
What is your personal feeling about it, trust your instinct. I am taking them on the Norte In May, after 85+ days over 3 caminos and in that a total of 40 minutes very soft rain and 20 minutes intense I feel I am owed some.
Good Luck
Mike