I count somewhere closer to 19 months from MS1 start to start of dedicated Step 1 period. Dell is 12 months to start of rotations.
Accounting for breaks, the actual time spent completing the preclinical curriculum is around 15 months at McGovern and around 11 months at Dell. Less difference than it seems at first glance. Dell has like a week of summer break, and McGovern has 10 weeks. Also, McGovern starts beginning of August, while Dell starts beginning of July. Lastly, McGovern experiences an additional winter break during MS2, while Dell's preclinical period ends before MS2 begins.
In summary, it's 11 vs 15 months of actual preclinical class time, or 12 vs 19 months including all breaks. I've been looking at their actual academic calendars, as opposed to relying solely on the curriculum schematics. Dell is definitely as modern as they come, but McGovern isn't as old-school as some might think.