One of the differences is their own style to play the guitar. The way that Ray Toro plays his guitar is serious, strong, and sometimes crazy. In contrast, Frank Iero plays the guitar even crazier than his colleague, Frank has much energy, he always falls down while he is playing.
Another difference between these guitar players is their nationality. Even though both grew up in New Jersey, Ray is from Puerto Rico, but he moved with his family to U.S. when he was a baby. While Frank is American, he was born in Texas, but when he was in high school, he moved to New Jersey, and he is still living there.
Their physical appearance is also an important difference between them. Ray is tall, strong, and one aspect that makes him unique is his big afro hair. Unlike Ray, Frank is shorter and thinner than Ray, actually he is the shortest in the band, he has many tattoos in all his small body and his hair style changes many times, he can have long hair, short hair, or a crazy hair style.
Ray Toro and Frank Iero both are so different, but I think that the mixture of different styles makes the special sound of My Chemical Romance.