They are both fantastic exercises for complete pec work.
Advantages of dumbell press are mainly that as the dumbells are controlled individualy, there is no way of the dominant side taking over and 'carrying' the weaker side of the body (this can happen if not carefull with bench press)
Also, I would recommend dumbells over barbell work for those on mass building regimes training alone as they allow you to go to failure without a spotter. Doing so with a barbell just gets you trapped under it.

Both good. Choose which you prefer.
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