I used both together for a few months and here are my thoughts:
For starters, BPI does not have as good of an AA profile and is developed differently from LBAs. They come out to be about the same price per serving, but BPI does not have glycerol. LBA's are already made and you just have to pour it down your throat...no mixing, no shakes, no refrigeration, etc. BPI does not mix easily and has a very salty taste...only the chocolate flavors are palatable...the fruity ones are horrible. You cannot beat the convenience of LBAs..you can take them everywhere...whereas powders just suck to deal with.
Biggest difference and I cannot explain properly why: I get way more energy, strength, and better pumps with LBAs....I also stay much leaner with LBAs too.