Is \$V_A\$ or \$V_B\$ the inverting input here?
Pick one of the inputs and follow the signal to the output.  This is easy and the result obvious if you understand the basics of how transistors work in a circuit.  If not, then that's what you should be asking about before trying to learn complete circuits.

When Va goes up, T1 takes more of the fixed Ibias current from T2.  In other words the current thru T1 increases.  The gate of M3 must be brought lower to allow this current to flow.  This lowers the gate of M4, which increases the current thru it, which increases the current thru R, which raises the output voltage.  From the Vout result for the Va input, it is now obvious whether Va is the inverting or non-inverting input.

From the comments I see there is confusion about basic transistor operation.  The gate of M3 must go lower to increase the current thru M3 because that's how P channel FETs work.  That is also the polarity assumed by how M3 is connected to T1.