I recently pitched the 11 year old against the ten year old in a comprehension race, assuming that the eleven year old would win, even though he is a physically slow reader. I was right, the practice he has had over school the last year on learning inference and reading between the lines, a greater development of empathy and mature reading, stood in his favour and although he guessed two at the end he only got one wrong. The ten year old was very quick, but made three mistakes, two of which he corrected with a quick glance and a sigh.
I would opt for teaching to read carefully and systematically, as this is the proper and useful way of teaching and learning comprehension, rushing through it goes against the grain and may form bad habits. His accuracy will ensure a good mark, but you can just tell him to not worry about getting stuck and move on after thigh seconds.
Obviously the test was not fair, but I haven't got twins to experiment on.