i just got a great deal on a ko pro ex-1 mars. they have just as many if not more features than the m8 and 3pk. it also uses modules like the others. the reciever comes with it is very tiny. the radio also uses "levels", basicaly groupings of functions that allow you to choose what "level" you want and not have to scroll throught 32967386 functions you dont' need. IMO the mars look the best. I got the original mars, but the R edition looks even better, but don't believe the 40% faster bs.
anyway... before you buy a radio you should go to your LHS and feel the radio.. see if it's comfortable, if the buttons are easily accessible, if it's heavy, etc. what it really comes down to is: ergonomics, looks, and ease of use. they really all have the same functions.