Like does this ticket takes an hour for X and a day for Y.
Out of context, comparisons like this are meaningless. Maybe the ticket took a long time for Y because he was assigned 30 tickets and spent most of the day suffering paralysis of choice, maybe that particular subject is difficult for him but he has other strengths. When you blamed him for it his knee-jerk response was to get defensive and make excuses (eg personal life problems).
Either way that shows that the employee is not good, if a person can't handle to do his/her own tasks one by one that person should not be work as a developer. BTW generally assigned person decides how long will it take to finish a task (a task can't take longer than 4+ hours if it's needs to be split into smaller chunks)
Out of context, comparisons like this are meaningless. Maybe the ticket took a long time for Y because he was assigned 30 tickets and spent most of the day suffering paralysis of choice, maybe that particular subject is difficult for him but he has other strengths. When you blamed him for it his knee-jerk response was to get defensive and make excuses (eg personal life problems).