What is the difference between declining payouts and setting @null to 100% beneficiary on a Hive post?

In my time posting on Hive I've found there's two ways to avoid receiving author rewards:

1. You can decline them completely
2. Or you can set Hive account@null as the 100% beneficiary to the post

Using Ecency web:

_{Decling payout}

_{Setting Hive account@null to 100% beneficiary}

So, what is the difference between these two methods, at the blockchain level?

Are they even different? Or is it just a case of there being two ways to use the GUI to get the same result?

I know that ultimately the author gets nothing no matter which option is used, but what about more broadly? I feel the code must run differently in each case, but how?

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