The biggest problem I've had at Vin Phat is language. Some of the staff, just do not speak much English. That hampers things a bit. The other problem, similar to what you've experienced, is that you are at the mercy of what's there. When lived nearby, and watched the building of Vin Phat, I got excited about idea of fresh croissants for breakfast. I duly arrived on opening day for such, only to learn that the croissants would not be there until the afternoon. Such is life at VP.
That said, I can typically get a banh mi to my liking at any hour. What I do, is walk around the cash register to poke around in back. Yea, they get a bit nervous, but tolerate me. I look for what looks good right then. It might be a bowl of grilled pork--this is what I got about a month ago or some small meatballs or whatever (and there is always the standard "dac bien" with ear and pate). With the prodding and pointing, I get something tha makes me happy.
I think the banh mi at VP are ever so slightly better (than Bale), but this is perhaps a preference for the underdog than real side by side comparision. I generally just go to the place I happen to be closest.
Rob