Marra and Fagan, the only two candidates to secure enough nominations to stand, are vying to replace Anas Sarwar after he announced he was joining Andy Burnham’s UK government via the House of Lords.
Monica Lennon also wanted to stand, but failed to secure enough support from fellow Labour MSPs.
The candidates were asked for their views on the drilling licences by Press Association after a hustings in Stirling before voting in the contest begins on Monday.
Marra said the issue was “finely balanced” but he believed oil and gas could be produced in a cleaner way in the UK rather than by importing from abroad.
He said: “I want to see that decision as soon as possible, but I know that it’s a challenging decision for the UK government.”
Drilling would be “vital” for the north-east of Scotland as well as boosting public finances, he added.
“We need to move faster to make sure we can secure proper investment in the North Sea,” he said.