When my boys were looking at schools they were debating the same options. You can find lower level D1 programs where the coach is flexible with a swimmers practice schedule. Have extra time available for the swimmer to swim his yardage by himself at an off time. Other coaches will not be so flexible. A great question to ask the coach is how many premed/science majors have gone through their swim program. If that number is not very large, that program probably will not be a good fit. For my boys, they selected a school in the NESCAC Conference as that was the best of both worlds for them. Best of luck, you will find a situation that will work best for your son.