SQL Server Backup Schedule Overlap
First step: Understand how backups really work. The main things to understand:


Log backups after SQL Server 2000 can be taken concurrently during full and differential backups. The only thing to remember is during that timeframe the log will not be cleared until that full or differential backup completes.
Full and differential backups that collide will cause whichever backup started first to take precedence, the second backup will wait in line until prior backup is completed. So if you have a FULL backup running, and a DIFF backup starts, that DIFF backup will wait until the FULL is complete. I do believe it should be the same for the opposite as well.


Second Step: Whichever backup plan you choose ensure it meets the recovery requirements for the application AND/OR the business.

So while either schedule will work the schedule 2 will likely lessen the amount of IO activity that is caused when the backups overlap. It would based on the size of the database and how much activity SQL Server has to backup during the differential and log backups. Depending on how you setup schedule 1 you could end up with all three backups trying to occur at the same time frame.