Are you staying onsite or offsite for your WDW park days?
If you’re onsite, your LL booking window begins 7 days from checkin, regardless of the ticket start date, so I’d buy the less expensive tickets.
If you’re staying offsite, your LL booking window begins 3 days before the ticket start date, not 7, so in that case you’ll have to decide whether the extra day of booking is worth $100 to you.