MARC is also routinely late because they have to sit behind Amtrak trains that are running late. And an Amtrak train that is 15 minutes late will get to D.C. in the same total time as a MARC train that's on time. Also, MARC is sometimes delayed leaving DC, while the 188 Amtrak always leaves D.C. on time. (Even the one that derailed and killed a bunch of people after I got off at Baltimore, left D.C. at 7:10 on the nose.)