Earlier is alwways better, statistically speaking, but an outstanding application is less likely to lack proper attention. When are you planning to take the MCAT?
You could always submit some weeks before the score is due back to be sure the entire application is ready to be viewed by schools as soon as the score returns.
If you are not confident of the score, you can submit to only one school just so verification proceeds. When the score is back, add other schools based on your competitiveness. Newly added schools get the entire application within a business day.