LS= Longest gears, best highway drive, best gas mileage, worst performance
GSR=Medium gears (not too long, not too short), Decent highway drive, Decent gas mileage, Best all around trans.
B16= Shortest of the 3, something around 4.5k rpm normal highway driving, Highways kill your mileage, not the best street trans (acceptable) but perfect for the track.
It also depends on what your doing with the car, People will say the Ls trans is good for boost..it really isn't unless you are trying to do like 175 mph, it was made for gas mileage.