Based on their last fights I voted Brook by decisiom but he might win by ko. Alexander should have KOed Bailey as so many others have done, but he took the safe way to victory. Brook will make him fight hard. Brook seems to be improving but Alexander seems to stay about the same, a good fighter but nothing really special.
I got Brook by decision too, but there's always that risk of a bad judging so I wouldn't be surprised if he won pretty convcingly but somehow got robbed.