There may be good reasons to prefer Paris over London, but weather is not one of them.
Here is a comparison between London and Paris weather data taken form two different sources.
Source 1: 30 year averages (1961-1990) from http://www.metoffice.gov.uk/climate/uk, http://www.meteomedia.com
Source 2: http://www.climatetemp.info
An end to the weather debate: it rains just as much in Paris as it does in London.
Whether comparing wet days, rainfall, humidity, or temperature London and Paris are similar. The one noticeable difference between London and Paris is the amount of sunlight each city gets.
Thank you Francine for the research!