What they share
Both are short names with strong single-vowel sounds. Both travel well internationally. Both work as full given names without begging for a nickname, which gives them a certain confidence classical long names don't share.
Pick Noah if…
Pick Noah for the biblical gravity. Noah means 'rest' in Hebrew and carries the weight of the flood narrative. It sits between tradition and modernity with unusual ease.
Pick Liam if…
Pick Liam for the Celtic warmth. Liam is a contracted form of the Irish Uilliam (William) and means 'strong-willed protector'. It feels friendly and grounded in a way Noah, with its scriptural weight, does not.