Difference between tri-state buffer and inverting tri-state buffer
Mostly, they are the same thing with or without an inverter.

Construction-wise, the simple buffer designs are naturally inverting, so the non-inverting ones have to have an extra layer of logic to invert the signal an additional time. 

This leads to both larger silicon area and longer signal path through the inverter.

With both parameters historically being critical and with the inverting design often being slightly more versatile (you can use it as a buffer, tri-state, and/or an inverter), both options were offered.