In the BJT case, why is it that the upper 3-dB frequency of a differential amplifier with a current-mirror load (1st picture) is lower than that of a differential amplifier with a purely resistive load (2nd picture)?

![Differential Amp. with Active Load](https://ez.analog.com/resized-image/__size/320x240/__key/communityserver-discussions-components-files/344/pastedimage1545563174268v1.png)

![Differential Amp. with Resistive Load](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Differential_amplifier_long-tailed_pair.svg/220px-Differential_amplifier_long-tailed_pair.svg.png)