My actual argument would be to do real usability testing to see whether either of the options (more animations; less animations) helps, on average, if made the default.
An analogy: the way we use capital letters in English helps to guide and reorient the eyes of people who are dyslexic. But English's capital letters also help in the same way—just to a lesser degree—the people who aren't dyslexic. It turns out that capital letters are just a good idea on average, like e.g. the wheelchair ramps built into sidewalk curbs.
Now, there are probably at least a few people in the world who can read English text better without capital letters for whatever strange reason. But if the average person can read better with them there, then it's better to enable them and make disabling them an option, rather than to disable them and make enabling them an option. The average person, not thinking of themselves as needing assistance, wouldn't look in the options for an "enable capital letters" option. And so the average person, who could have been helped by the assistance, would have QALY left on the table—and that's a large amount of QALY when multiplied by the number of "average" people, compared to the two groups that have specific, recognized problems that they'll know usually have solutions in options menus.
An analogy: the way we use capital letters in English helps to guide and reorient the eyes of people who are dyslexic. But English's capital letters also help in the same way—just to a lesser degree—the people who aren't dyslexic. It turns out that capital letters are just a good idea on average, like e.g. the wheelchair ramps built into sidewalk curbs.
Now, there are probably at least a few people in the world who can read English text better without capital letters for whatever strange reason. But if the average person can read better with them there, then it's better to enable them and make disabling them an option, rather than to disable them and make enabling them an option. The average person, not thinking of themselves as needing assistance, wouldn't look in the options for an "enable capital letters" option. And so the average person, who could have been helped by the assistance, would have QALY left on the table—and that's a large amount of QALY when multiplied by the number of "average" people, compared to the two groups that have specific, recognized problems that they'll know usually have solutions in options menus.