Outside one of the few known flukes or risky tactics, for plain ol reservations the boarding positions are doled out in this order:
Business Select
A List Preferred Members
A List Members
EBCI Purchasers
THEN:
Everyone else that is left fighting for check in at the T-24 mark
So chances are slim to none that you will get a better check in at T-24 than you will with EBCI.
Only BS and T-24 checkins are dependent on chronological check in time...A, A+, and EBCI are pre assigned through WN's mystery algorithms.