Aquino showed enough last year for this limited role. RH bat against LH pitching with occasional starts. He’s 26, I see no utility having him off-roster this year.
But Ervin is more experienced, out of options, had a good year against lefties (as did AA), so Phil likely gets the job. Fine, both are worthy, but there’s a redundancy, not ideal.
Reds have a glut of OF talent, mostly guys suited for the corners, not perfect team balance - although you never know where depth will be needed given COVID risks.