based on past years, the day before is not packed in the park.
once tday comes and the days after, you will see more crowds.
check the calendar on the UO website and see what the ep charge is for the day before t day.
if it is $25.xx and under, that is an indicator of a low crowd day.
recheck a couple of weeks before you go and see if it is changed.
i always advise homies to wait and buy the ep when they are in the park unless you know in advance it will be a high crowd day based on the info on the UO calendar.
you can buy the epp at gs, and in the parks at the main merch stores.
once you buy the epp, they are yours.
they are nonrefundable.
wait until you are there to make a decision.
you might be able to get a lot done in one park and then go to the other park.
if that park is crowded and you have limited time, then buy the epp for that park.