Both were sought after painters by the Italian and Hapsburg royalty and the Catholic Church. Of the two, Titian was more appreciated for his style and work. Caravaggio was the more experimental of the two, building on Titian's work, but amping it up. Either by going very Baroque with overwhelming details and colors or, for the religious and violent works, going very dark into light and shadows for emotional effect.
Oddly for the time, Caravaggio didn't make a working sketch first. He used live models - often the same, see the young man in Boy with a Basket of Fruit, The Musicians (top of page), David Holding Head of Goliath and St. John the Baptist. This is Cecco - one of his models (and assumed lover).
There is a lot of fascinating underlying stories in Caravaggio's work. You can get some interesting facts here about him 7 Interesting Facts About Caravaggio.
But I love him because of two things. First his interesting style that didn't employ brush strokes, but used light and dark so amazingly. Second, his overwhelming style that is purposely overwrought and overdone. It is the first recognizable use of hyper-realism (at least to me). Like these below...