Indoor track is my favorite season. I've lived in the Boston area my whole life and I've run on all three tracks (4 if you count the old BU) countless times through HS, college and beyond. I agree with another poster that Reggie is superior for distance and Harvard better for sprints. I like the air quality in Reggie better also. I've had numerous back problems during my life and for some reason my back always hurts when I run at Harvard. Perhaps the surface is harder.
Just for fun. I agree that BU new is far superior. BU old was also crazy fast and I can't explain why. The air in BU old was obviously horrible and I used to hack up a lung for 3 days after racing there. But I ran my best times through college at BU old so I love it (I even kept a piece of the track as a memento). My current mile PR was run at Harvard post collegiate. 1K PR at BU old in college. 3K PR at Reggie and 5K PR at BU.