In the Miracle Worker, do you think Helen's worst handicap is deafness or blindness?
Wow, it's hard to choose, the combination of the two makes everything so difficult. In Act II, the fight between Annie and the Captain begins because Helen keeps breaking things while he is trying to carry on a conversation. If she had seen them, she might not have broken them. Or maybe she would have, because the destructive acts seem to be more borne out of frustration that "oops," you know?
Hearing might have made life easier for Helen because she could have understood the names of things and thus more easily understood how objects relate to people (and vice-versa) as well as their purposes.
Your question is really too subjective to be answered in a question-and-answer forum such as this. It calls for the reader's personal opinion. You might want to put yourself in Helen Keller's shoes and imagine what would have been worse for her--not being able to see a songbird, for instance, or not being able to hear its song. Which would you consider the worst handicap?