Root: best comeback you've witnessed
Brass Lancashire vs Brass Birmingham is a comparison worth making carefully. Lancashire is faster, meaner, and rewards aggressive building in ways Birmingham softens. The coal glut that Lancashire suffers — where too much coal floods the market and building iron becomes impossible — is a real design issue that Birmingham's merchant tiles address.
Birmingham adds more player count flexibility, the merchant bonus tiles, and more map variety for the railway era. The design improvements are real. But Lancashire has a stripped-down efficiency that experienced Brass players appreciate for its directness.
For a first Brass purchase: Birmingham without question. For players who love Birmingham and want more: Lancashire is different enough to be worth owning. For players who want only one: Birmingham.