Levain build query! - First ever sourdough bake

Hi,

I am attempting my first ever sourdough bake this week. My starter is 6 days old and has some really nice activity and had it's first rise and fall today .

I am planning on doing a small loaf using the 1:2:3 method. My query is ratios for my levain build. I want 120g of levain for my recipe. Do i use;

a) 20g mature starter + 50g water + 50g flour

or

b) 40g mature starter + 40g water + 40g flour

Is there a benefit to using one over the other or does it matter?

Hope someone can shed some light on this! 

Many thanks :)