Quintilian, Institutio Oratoria 10.105:
Not undeservedly was Cicero said by his contemporaries to be king in the courts, and he maintained that among his posterity such that ‘Cicero’ seems like a word for eloquence, and not the name of a man. Let us then look at him, and let it be placed as an example before us that one may know that they have achieved knowledge when they find much pleasure in Cicero.
There is a lot of invention in Asinius Pollio, and even so much attention to detail that some think it seems excessive; there is also enough of consideration and mind in him. He is so far from the resplendence and pleasantness of Cicero that he could seem to be from a previous generation. But Messala is resplendent and shining and in a certain way making a pretense of his nobility in speaking, though possessed of lesser powers.
If only Gaius Caesar had stayed away from the forum, there would have been no one else whose name could be set against Cicero’s. There was such great force in him, such acumen, such quickness, that he appears to have spoken with the same vigor with which he waged war. Yet he decorated all of what he wrote with a marvelous elegance of speech, of to which he was rightly devoted.
Quare non inmerito ab hominibus aetatis suae regnare in iudiciis dictus est, apud posteros vero id consecutus ut Cicero iam non hominis nomen sed eloquentiae habeatur. hunc igitur spectemus, hoc propositum nobis sit exemplum, ille se profecisse sciat cui Cicero valde placebit. Multa in Asinio Pollione inventio, summa diligentia, adeo ut quibusdam etiam nimia videatur, et consilii et animi satis: a nitore et iucunditate Ciceronis ita longe abest ut videri possit saeculo prior. At Messala nitidus et candidus et quodam modo praeferens in dicendo nobilitatem suam, viribus minor. C. vero Caesar si foro tantum vacasset, non alius ex nostris contra Ciceronem nominaretur: tanta in eo vis est, id acumen, ea concitatio, ut illum eodem animo dixisse quo bellavit appareat; exornat tamen haec omnia mira sermonis, cuius proprie studiosus fuit, elegantia.