Since your Purchase Order is generally sent to a Vendor with a single Ship-to Address (comes from the Header) on it, the recommended approach is to have the Line Location match the Header Location; meaning you would have two POs in this scenario.
Ignoring that issue, the Location on the Lines wins in terms of Item Ledger and costing, so your Header Location doesn't impact either of the lines. The Header Location is mainly to auto-populate the Line's Location AND to update the Ship-To Address on the paperwork.
Best Regards,
Ben Baxter
Accent Software Inc