Pant was named in India's 15-member squad for the June 1-29 tournament on the back of impressive performances in the Indian Premier League (IPL) after his comeback following a near-fatal car accident in December 2022.
However, India's selectors kept their options open with Samson also making the squad.
"I think only one of them will be in the starting side and whoever it is, India must back him... both have equal quality," Gambhir, who played an important role in India's World Cup triumph in 2007, told Sportskeeda.
"It's touch and go but I'd start with Rishabh because he's a left-hander and a natural middle-order batsman. Sanju in the IPL has batted at number three, but India's top order is fixed.
"Rishabh has batted at number five, six and seven. India need a wicketkeeper in that position as compared to a top-three batsman. A left-hander in the middle-order gives you that left-hand-right-hand combination."
Delhi Capitals skipper Pant scored 446 runs from 13 matches in the IPL this season, with a 23-ball 33 in his team's 19-run victory over Lucknow Super Giants on Tuesday.
His Rajasthan Royals counterpart Samson has also done well with the bat with 486 runs from 12 games and can still add to his tally.
"If India see that Sanju can score more runs at number six or seven, they could go with him as well," Gambhir said.
Delhi's win means Rajasthan are assured of a top-four spot along with leaders Kolkata Knight Riders, leaving two playoff places up for grabs.
