Finally found a good banh mi, far better than Lee's Sandwich or Banh Mi Che Cali's banh mi, which have always felt vaguely dissatisfying, though pretty good.
Buu Dien, in Chinatown.
The bread ain't as fresh, but the meats and fillings are genuinely lively. Makes Lee's fillings seem bland and Oscar Meyer-ish in comparison. Where Lee's and BMCC have all same-ish sorts of meats, Buu Dien's dac biet (the usual cold-cut assemblage) has satsifyingly different stuff - the tendon-y cut, cool and chewy, the meaty stuff, the sweet-ish stuff, and the definite presence of crap pate, which is essential to the experience.
Good nem nuong (semi-preserved pork meat-semi-ball) sandwich, too.
Be warned: pricier than Lees, by a major margin. Where Lee's dac biet is a mere $1.50, Buu Dien charges a whopping $1.75. But if you can spare the extra cash...