Current Starved inverter with current sources connected to Vout node
In diagram 'b' I would expect M3 and M4 to have higher gain from Vin to Vout and less Miller feedback as they are separated from the output by M1 and M2.
This lower feedback will also result in less capacitance loading on the previous stage giving a faster transition time. Possibly less energy consumption per transition (lower power consumption when cycling).
The voltage levels will be almost identical.