Valve choices

MOPAROFFICIAL said
3/8 to 8mm, world of diff.
8 to 7? Splitting hairs.
Am I still interested if its cost effective and readily available, sure. Thanks.

Actually doing the math, the 8mm is ~28.5% less stem mass & pocket volume displaced than a 3/8" stem, 7mm is ~55% less...more than a hair..