Sigh...I really don't want to explain it in detail but I will for special people like you. Ok, so BSM = lets you hit people while sprinting, new 1.7 sprint update = Guess what! Doesn't let you hit people while sprinting. BSM = after you press the dedicated sprint button, you don't hold it or anything after you press it every time you press W it automatically sprints, with the new 1.7 update you have to press w then press the button for sprint, if you hit a block and you press W, you will not automatically sprint like BSM, you will have to press w then the dedicated sprint button again. also B.S.M. has many features like permanent sneaking and some flying options I think.
TL;DR BSM=Permanent Sprint, Hit people while sprinting, other features = COMPLETELY different to the new 1.7 update.
I hope you understand.