I agree that either option is better. This conversation arose out of another thread where those two options were alternatives that
@Schmendr1ck tried with his group, but blinding off was a PITA and one player—not even a habitually tardy one—was very vocally opposed to a late penalty / on-time bonus.
The vocal player even insisted that the late penalty was unfair. In the end, the game went with the structure I'm describing here, which I find to be unfair in the opposite direction. It incentives people to show up late and opens up the buy-in process to (minor, probably misled) attempts at advantage play.
This is not to overly criticize ol' Schmendy. You gotta do what makes your players happy, and if they're going to stage a mutiny over the other way, it's not really a decision. I'm mainly critical of the vocal player whose less-than-nuanced understanding of fairness forced his hand.