I think the simpsons adapt to the current events in our world and make the devastating funny and acceptable. I think that futurama is the life of a low life that has fun with other low lifes, and because we as humans like to make fun of people, or see others suffer, it is humorous.
I think both are funny, but I prefer the simpsons because it is more outlandish and slap stick, my kind of comedy. I also enjoy that they put more thinking into the stories and the progression even after 25 years of being on the air. They must be doing something right to be on the American television broadcasts for that long, right?