For decades, each time a U.S.-based law firm has hired a London partner from a U.K. rival, the response has been the same: U.S. firms may pay more but U.K. firms have a better culture.

The logic behind the stance is that U.S. firms are more likely to have a merit-based remuneration structure as well as higher billable hours targets. When the hard times come, U.K. firms argue, U.S. firms are less likely to be collegiate.