Leaders of Partners HealthCare and Hallmark Health System said their planned alliance will lead to more integrated medical care, but not all of the community leaders and residents at a hearing Wednesday were convinced the deal will be good for patients. The proposed takeover of Hallmark, which owns Lawrence Memorial Hospital in Medford and Melrose-Wakefield Hospital, will allow Boston-based Partners "to invest both substantial financial and clinical resources in Hallmark Health," said Dr. David Torchiana, head of the Partners-owned Massachusetts General Physicians Organization. He spoke during a hearing hosted by the state Department of Public Health at Tufts University.