Dalton Investments, a $3.4 billion U.S. investment firm, says it’s still on the fence over whether to support Shinsei Bank Ltd.’s management or SBI Holdings Inc. in the battle for control of the Japanese lender.

Neither side has given a convincing argument for its backing, said Jamie Rosenwald, a Dalton co-founder and portfolio manager.

Shinsei should have found an alternative buyer willing to pay more, while SBI should bid for the entire company rather than just a partial stake, he said.