The strain of yeast has an influence on flavor, a fact that anyone who has made beer or wine can attest. I have tried making bread with champagne yeast and can report that although neither beer nor champagne made with baker's yeast is fit to drink, the change in flavor of bread is very subtle and barely, if at all, noticable. I think this is due to the fact that the yeast in bread is killed and the alcohol it generates driven off by the high baking temperature. Wine and beer brewing is done at around room temperature once the yeast has been added, so that the yeast is not killed (it just goes dormant when a sufficiently high alcohol level is reached) and the alcohol it produces together with the other organics produced during fermentation (that, for example, give some beers a 'buttery' flavor) are destroyed in the heat of baking.
