Two years back, they were the most promising leaders in Asia, set to revamp a pair of perennial underperformers that account for a fifth of the world's population.

Now Indian Prime Minister Narendra Modi and Indonesia President Joko Widodo, known as Jokowi, are seeking to revive momentum for reform plans that got derailed in the wake of watershed election victories. For investors, while Modi has been the better bet so far, it's hard to see who has the better chance at success.

"Both impress in different ways — and disappoint," Hugh Young, managing director for Asia at Aberdeen Asset Management PLC. "One man is rarely the solution to a country's problems."