Boyzone: Managed by Louis Walsh, they were the pioneers of the modern Irish boy band, dominating the UK and Irish charts in the 90s with soulful ballads and covers. They paved the way for subsequent acts by proving that the “boy band” model could work outside the U.S.
Westlife: Also managed by Walsh (and Simon Cowell), Westlife surpassed their predecessors in terms of pure statistics, securing 14 number-one singles in the UK. They became the kings of the “key change” ballad, focusing almost entirely on soaring vocal harmonies.
Comparison: Boyzone had a bit more of a “street” or casual image in their early years, whereas Westlife was meticulously groomed for mass-market balladry. While Boyzone started the fire, Westlife became the more commercially enduring machine across Europe and Asia.