They wouldn’t. Assuming that both addresses are the same type (transparent, Sprout, or Sapling), the transaction that spends from address 2 would be larger.
This is currently the de-facto case for purely-transparent transactions:
zcashd inherited the default fee-setting logic from Bitcoin Core 0.11.2 and we haven’t altered it (and other transaction-creating entities such as wallets I assume just use the same logic they use for other cybercoins).
For shielded transactions,
zcashd defaults to 0.0001 ZEC for privacy: choosing a specific fee leaks information (both about the user and the software they used to create the transaction). There are plans to alter this to have some level of variability, but that variability will only depend on information that is already public (e.g. the visible size of transactions), and would not replicate the behaviour of Bitcoin-style fee selection where the fee is set based on expected time-to-mined, because that leaks information about the view of the network that the transaction creator has.