The real question here isn't aesthetic. It's which has a bigger impact on performance, the drag created by the hole or the grams added by the plug. Any other concerns are a very distant second.
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A race bike in any era is a highly personal choice that at its "best" balances the requirements of fit, weight, handling, durability and cost tempered by the willingness to toss it and oneself down the pavement at considerable speed. ~Bandera