They are diffferent discs, both with the same top. The TL will have a little more high-speed turn and less low-speed fade.
I'm not sure if the bottom is from a Leopard (Dave D has said no). There are several other "L" discs from Innova which are not the same diameter as the Leopard (e.g., Starfire-L, Firebird-L), so "L" doesn't necessarily denote a Leopard bottom.
The L stands for less over-stable and longer. I know what the difference is
between a TeeBird and a TeeBird-L. What I was looking for and what I found out is that
the first pro TeeBirds were just plain TeeBirds and not TeeBird-Ls labled as plain TeeBirds.
Innova made regular Teebirds in the first run for a few months and then changed to making just TeeBird-Ls for the pro version.