Would be slightly different, no? "Bạn té" would be more "you [trip and] fall" where "bạn ngã" would be more "you fall [for unclear reasons]." Same effect; slightly different connotations. And anyways, I always have morbid connotations when associating "ngã" with a person since I often hear it used euphemistically (for death - like a fallen soldier).
I believe "to trip and almost fall" means "vấp" and "to trip and fall" means "vấp ngã" or "vấp té".
"Ngã" and "té" mean the same thing. "ngã" [Northern dialects] = "té" [Southern dialects] = to fall
"to fall flat on one's face" = ngã/té dập mặt
Oh my... I'm taking the placement test right now and a lot of the questions are throwing me off because I think it's all northern Vietnamese and my parents are southern Vietnamese!! This is truly weird to experience, but I'm pretty sure bạn means friend in both north and south... but I guess the Viet program is still in beta anyways right?