Shaykh Al Uthaymeen said:
It is befitting that the preference be given to the one with a good voice in regards to the Athaan, and a good voice is with three matters:

Good presentation, good tone, and strong voice 
If these three are gathered in a Muathin then it is the most complete that can be.
Explanation of Bulughul Maraam 2/97 
Majid Jawed Al Afghaanee