“What is the difference between a L-port and a T-Port Ball Valve?”
With a L-port the ball is drilled from two different sides (90 degrees) and the drilling resembles the shape of an L. The T-port valve is basically the L-port valve, but the ball is drilled all the way through in one direction. So the drilling of the ball resembles the shape of the letter T.
With a L-port, the middle port is the common port, and with a T-port, one of the side ports is the common port. But this assumes you want to use a T-port ball to divert as you would an L-port ball valve.