BrianU's point on Power attribute stands under all-else-being-equal conditions...
If you are controlling the in-game player, there may be certain factors (even weird things like batting stance, how comfortable/pressed you feel with players you feel attachment to) that affect how well you hit with the guy, but that's basically on you, and you are being the factor. When the player is controlled by CPU, it mostly becomes about attributes.
This is even more so when games are simmed (where some of the attributes that provide more varied characters to players don't factor in, like individual pitch attributes).