I always pick for the bottom edge of the armpit on what i think is a nervous deer, BUT one time my arrow went right there and the buck never even dropped,,clean miss but when he jumpped he broke my Arrow then stopped and giggled at me before ducking back into the swamp.
a clean miss is a good miss and good lesson!
make sure your bow is as quiet as possible and pick spots lower if your deer seem nervous,, I've seen countless videos of where deer drop up to a foot in milliseconds and beat compound arrows.