Travel should be heavier on Easter than on the previous day. Many families will be completing a week's vacation that day, since kids in about 22 states will be completing Easter vacation on April 8 (Easter) or April 9.
Only about 11 states start school vacation on Easter weekend and most of those vacation periods include Good Friday (April 6), meaning that those families might well start travel before Saturday. (There is some duplication in the state tally, because some states have varying vacation periods, at local option.)
As for airfares, I think you'll find the fares to be about the same for both days as long as you get your tickets before Thanksgiving or thereabouts. Although it's too early to reserve for next Easter, you can test fares for your specific routing by sampling fares (as an example) for various dates for the year-end holidays.