hybrid-π model VS T-Model for MOSFET and BJT
I strongly recommend NOT to use the T-model. I hesitate to classify it as "wrong" - but very close! At least it is confusing - unless you know exactly what you are doing. However, anybody who does exactly know what he is doing does not need any such model at all.

Explanation/justification: 

(1) The transconductance gm appears as a resistor r=1/gm between the base node and the emitter node. This is not in accordance with physical reality because gm is a TRANSconductance and connects input voltage and output current. Hence - it must not be modeled as a resistor (two-pole element).

(2) Looking into the model from the emitter (base at ground) the input resistance is 1/gm (correct); however, looking into the model from the base node (common emitter) it seems that the input resistance also is 1/gm - but this is wrong!

(3) In case of common emitter topologies, the model is valid for current injection into the base only (current source at the base node). This is not in accordance with most of the applications which use signa VOLTAGES. 

(4) In case of emitter degeneration (Resistor RE in the emitter path) we have two resistive parts in series: r=1/gm and RE. Consequently, the denominator of the gain formula contains the sum (r+RE). This expression can be misinterpreted because one might think that both parts play the same role (e.g. feedback). But, of course, that is not the case.

(5) My conclusion: I do not like the T-model at all. For my opinion, it does not help to understand what`s going on within a transistor - the contrary is true! Hence, I cannot see one single advantage of this model if compared with the classical (pi and h) small-signal models.