That doesn't mean anything. Asking "which is faster" is fact retrieval, which LLMs are bad at unless they've been trained on those specific facts. This is why hallucinations are so prevalent: LLMs learn rules better than they learn facts.

Regardless of how the base64 processing is done (which is really not something you can speculate much on, unless you've specifically researched it -- have you?), my point is that it does degrade the output significantly while still processing things within a reasonable model of the world. Doing this is a rather reliable way of detaching the ability to speak from the ability to reason.