The layoffs, which are slated to save over $200 million from MGB’s $10.3 billion salary and benefits expenses, are part of a broader joining of services across the sprawling 12-hospital network. To many, the consolidation is a critical, albeit challenging, step the system has put off since Mass. General came together with Brigham and Women’s Hospital in 1994. But much as many might agree on the necessity of the work, opinions differ on whether the specific decisions that executives are making are the right ones.