Monk made the biggest contribution, compositionally. Range of intensity and darkness to the most quirky sense of humor of anyone on this list.
Coltrane was the most god-bothered, focused soloist. Actually my favorite on this list if I'm to judge by what I reach for in my CD collection, but I think a tighter range than the others. (That's too facile -- I know there's a lot of distance between "Ballands" and "Ascension", for example).
Miles was also a great soloist, more conceptual changes as a bandleader, trying to find cutting edge of the music all the time. Led and schooled more than one stable band of geniuses, and had a totally unique timbre that became so influential as to become one of the standard approaches to the instrument.
Mingus was also a great composer, clearly Ellington-based but generally, more modernized, with a freer sense of time. Absolutely the pinnacle as an instrumentalist, too, like Coltrane on his instrument.
It's hard to pick anyone, given love for all of their music, and given differences in what they had on offer as composers, soloists, bandleaders. Couldn't really compare Duke Ellington to Charlie Parker either, y'know?