I will say that Madrid's metro system is much newer, cleaner and brighter than Paris's. The cars on the metro trains are more spacious too. But Madrid's underground is heated (or at least it is hot), which may sound good until you realize that many people get sick in the winter because they're going from freezing cold outside to too hot inside. You have to put on scarf and coat and hat and gloves to walk to the metro, and then you have to take them all off when you get on the train and then you stand there with sweat dripping down your back, and of course the sweat cools almost instantly when you step outside and then you have to put all your acoutrements back on... It's a vicious cycle. The Paris metro is pretty much the same temperature as the outdoors, which means you keep all your clothes on and aren't subjected to such extreme temperature changes throughout the day.
The thing that really bugged me about Paris was that I found it impossible to take a picture that could capture the grandeur and beauty of the city. I guess you could say that Paris isn't very photogenic. Even though Madrid is uglier overall (in my opinion), it's still possible to take beautiful pictures. It would take me days, perhaps even weeks, to get the hang of it in Paris. Or maybe it's not possible at all.
One of the realizations I'm coming to about Madrid (and possibly Spain in general though at this point I'm not prepared to go that far) is that the culture is based on blue-collar culture. The food is made from every part of the animal except the good parts, and the cheapest ingredients, such as potatoes, tomatoes and eggs, are the staples of the madrileño diet. Everyone from the 5 year old child to the 90 year old grandmother swears constantly. They smoke everywhere and throw their trash and cigarette butts onto the café floors. For fun people drink cheap beer in their local bars or they visit their family's village on the weekends. They stand around on street corners or in cafés gossiping about their neighbors and arguing politics. It's a culture that values family and friendship and enjoying the present moment while respecting traditions of the past. They don't care much for art or philosophy. Madrid is not a city of innovators; if it isn't broken, they don't fix it. And sometimes they don't fix it even when it is broken if they decide they can get along well enough without it. While I admit that I could stand to learn how to better enjoy a present moment, drinking cheap beer while eating leftover parts of the pig and gossiping about neighbors is not my idea of a good time.
Paris, on the other hand, seems to me more concerned with higher culture. There is something elegant about Paris and its people. They seem to care more about aesthetics, both on the street and in their restaurants. For fun people go out to dinner in clean, well-decorated restaurants or stroll along the river looking at used books or outdoor photography exhibits. They hold dinner parties and stay up talking until 4am. Paris is saturated with creative energy. Historically, the French have been at the forefront of art, fashion and intellectual movements. And whereas madrileños are proud of their cuisine without taking pride in it, the French have turned food into an art form.
In a way it's slightly unfair for me to try to compare Madrid and Paris because I have never lived in Paris. I'm very aware that my observations of Paris may be tainted by a romantic view, and there are many aspects of both cultures about which I am ignorant, but I've stated what I believe to be true. In the end it just boils down to the fact that I am more comfortable in Paris because its culture (or what I perceive to be its culture) is in better alignment with my values and interests than Madrid's is.