
If the show is on the Group system then you are best to enter the breed classes, and of course you can also enter the veteran. If you go BOB in the breed you can go on to compoete in the Group, whereas the Veteran winner can't go on if they didn't win their breed.
on a non group show, especially if the BIS judge is doing the varieties like Veteran, then I would go in the Veteran, and if you win, then you can still go forward under the judge who put him up, into BIS.
Of course you can still do both, and if you win BOB, and want to be sure of being able to compete4 further, then withdraw from the Veteran.
I never withdraw from varieties if the judge doing them is the Group judge, as if they don't like my dog in it's class, going in for Group or BIS wouldn't have been worthwhile anyway!