Yes, but that's cherry-picking. If you only look at the famous victories, of course the Marian legionaries are going to look good. When Marius first deployed his mules in Numidia, it didn't really alter the progress of the campaign. Yes, he later used them to decisively beat the Cimbri, but not before his consular colleague (presumably also using the new-model legionaries) was defeated. The victory was the work Marius, and his drive for training and discipline, not the new type of legionary.
And I don't believe that all Marian legions were trained to the same high standard. There was no standard because there was no standing army. The level of training would have depended entirely on how motivated the guy in charge was. During the civil wars, Roman legions were often hastily raised and unreliable formations.
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