I doubt that “how much” a difference a higher score makes is a question that can be answered. In general, a higher score is better than a lower score, until you at or above 1550 or so where you’re simply in the “top” scoring group. The difference between 1520 and 1550 is unlikely to be large. But every schools has a “last 10 students admitted” and “first 10 students declined”, and the differences between applicants at that level are extremely small.
It may be a question of how confident you are that you can score better, how much time you will invest to take it again, and what else you could do with that time.
Given that it’s in the very near future, that you’ve already registered and only get $10 back for canceling, and almost all schools allow score choice these days, I’d probably lean towards taking it.