upgrade master brake cylinder

The bore size is important for the amount of effort you have to apply.
Smaller bore gives you more " mechanical advantage/leverage" requiring less effort, often used when eliminating the power booster, and often preferred by " spirited" drivers.
The "look" is up to you.
My car, I've had since new, and I'm keeping it original, - to some, that look isn't important, and may prefer the modern look.
Both pumps work exactly the same .