WHAT REAL DIFFRENCE?

I SEE THAT MTH HAS NOW RELEASED 2 MORE VERSIONS OF THE R-26,ONE IN REDBIRD R-21 COLORS AND THE OTHER IN SILVER AND BLUE,AND AGAIN WITH THE KALE GREEN ONE.CAN ANYONE TELL ME, WHAT REAL DIFFRENCE IS THERE BETWEEN THE R-26 AND THE R-21,And R-17,BECAUSE TO ME.THEY ALL PRETTY MUCH LOOK THE SAME.BUT AM FOOL FOR THE BLUE AND SILVER SCHEME,AND I MIGHT GET THAT 1 SET.LET ME KNOW,THANX