Vanisha is already dubbed 'Woman of Steel' after joining the board of her dad Lakshmi's $80 billion global metals empire, and Holly gave up her medical career to join Virgin instead.
After earning a master's degree at the European Business School Vanisha is considered such a worthy successor to the Indian-born tycoon that US financial 'bible' Forbes magazine tips her to lead the family business to even greater success.
"She is just as hard as the steel on which her dad's empire is based. In fact, she's so good he almost had to plead with her to take a seat on the board," The Daily Star quoted a fellow director, as saying.
Vanisha, who tops the Forbes rankings of super-heiresses most likely to expand their fortunes, stands to inherit more than $51 billion.
While Holly, 27, stands to collect approximately $3.8 billion.
Qualified doctor Holly "may not have her father's thrill-seeking gene," says Forbes, "but she's well educated and grounded enough to take over control."
A third British-based beauty also figures: Canadian Alannah Weston, whose dad bought the department store chain Selfridges back in 2003.
Forbes' survey has been turned into an E!Entertainment television show titled The 20 Most Intriguing Billionaire Heiresses, to be broadcast later this month.