Rate of electrophilic bromination in aromatic nucleus

In Clayden, the increased rate of electrophillic aromatic substitution is explained by the stabilization of the intermediate through sigma conjugation. In Solomon & Frhyle, the same is explained through inductive effects.


Both the factors oppose each other in the following compounds: toluene, ethylbenzene, isopropylbenzene, and t-butylbenzene, respectively.


[![enter image description here](https://i.stack.imgur.com/sL2gH.png)](https://i.stack.imgur.com/sL2gH.png)


**My question:**



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> What should be the order of electrophillic aromatic substitution for the above molecules ?
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