If as the Union player if you choose Cross at Bruinsburg a major victory for the Union player will not end the campaign A Confederate major victory will still end the campaign as a Confederate win.
If the Union player elects to feint at Bruinsburg -effectively you end up having a one scenario campaign -it is basically replaying the Chickasaw Bayou situation.
As a Union player I will probably always pick the Cross at Bruinsburg option - I doubt the Confederates have much chance of achieving a Major Victory in this scenario -but I guess they can get one. I'm not saying if it is right or wrong (as a campaign design ... I mean I have an opinion, but this isn't really the place for that).
Vicksburg is probably my favourite title in the series - I once played Dale Blair at this one some years back - and it was literally on a knife edge -where I had to keep winning or he'd win the campaign (which in the larger Pleasant Hill scenario is really tough - since there is so much territory to cover - and the map has some really bad sight lines ( talk about needing to use your cavalry for screening ...
). I also won it the one time that I played the Confederates (I refused battle for several scenarios ... knowing that it would not end the campaign ... with the idea of conserving my forces)... then my opponent decided to go Vicksburg itself, so I had to fight - and well ... he lost. I guess that sort of happens with a series of uncoordinated assaults ... but I guess that isn't the point so much as - it was pretty good.
Just don't get stuck in the cycle of the one and done scenarios -as I can see where that would be somewhat less than enjoyable from players' standpoints.