SPRINGFIELD — A new analysis of a marijuana legalization effort says it’s unclear whether more or fewer people would go to prison under the proposal.What is clear is that the fiscal benefits of the idea outweigh the costs, according to the state agency that analyzes prison policies.Between decreased costs to local law enforcement and new tax revenue, two bills aimed at legalizing recreational marijuana use would have had a net benefit of between $170 million and $306 million had either of them gone into effect …