If money wasn't an object, I'd pick BU out of those three. If it was, I'd pick Rutgers.
My understanding is that the training at BU is "toolbox" meaning you don't just study one technique. Rutgers is mostly into Meisner Technique the first couple of years. That can be great If your son would be satisfied with it and I hear Kevin Kittle is a pretty amazing teacher although I hear the voice & speech person can be ... difficult. Not sure exactly what they do in Tisch ETW, but I believe they're known for turning out excellent physical actors who often have trouble with text (I know I'm speaking second hand.

). Of course an advantage there is that he could change studios after two years into one that covers anything he might find lacking.
At Rutgers, he'll spend his whole junior year in London studying at the Globe. At BU, he'll spend a semester in London studying at LAMDA. At Tisch, he'll have the option of studying abroad - a semester I believe - at various places including RADA.
Tisch is located in the second most influential city in the theatre world (behind London). Boston isn't too shabby, either, though. Then ... Well ... Rutgers is a short train ride away.
If he wants a lot of academics, Tisch wins hands down. If he doesn't, the Rutgers program is pretty much pure conservatory with only a minimum. I haven't looked at BU's curriculum in several years, but it seems like I remember it being somewhere in the middle.
Anyway, there's my two cents. Oh, and big congrats on having good choices!