Northeastern is a slightly shorter walk, particularly if you are exiting from the main station concourse. Northeastern also keeps you going in the right direction if you're heading inbound -- going to MFA is a slight doubleback.
Screenshots of Google Maps from a midpoint between the two ends of the station -- if you exit from the main coucourse, it becomes 4 min to Northeastern and 7 min to MFA, which definitely points to walking to Northeastern. (Also note that Google Maps appears to be inaccurate regarding the locations of crosswalks and the E Line platforms -- if you put in "Northeastern" as the transit stop, it sends you on a much more roundabout route.)
View attachment 27246
View attachment 27247
On a different note: I
really hope they extend/divert the 4, 92, 93, 111, 426, 428 and 450 to provide a transfer at Government Center instead of Haymarket. At the very least, they should extend the 111 and the 400 buses to terminate at Gov't Center instead, so they don't just dump their passengers at Haymarket and let them walk. The neighborhood map below is 10 years old, so some of the routes don't run anymore, but it gives you an idea of the area.