I cannot answer for what
@Busaholic meant but Brearley used his intellectual abilities and learning in his role as captain that I'm not sure that anyone before or since has. I believe that the Aussies choose the best eleven on ability as players then select the best captain from them. However, I would say that if Brearley was picked, he should be picked as captain, or not at all.
If Smith is being described as being inferior to Brearley, I'm not sure that this is an insult, most were. Some players make great captains, although average players, Jack Bond of Lancs for instance, and are well worth including in the team for their ability to motivate, think originally and just do the right thing at the right time. I don't know whether Smith fits that bill but Brearley had that in spades.