Hello! Welcome to the forums by the way.
As far as your question is concerned, I don't think adding or don't add preservatives would alter the taste of the syrup. Since it's extremely sweet with 5lb of sugar per gallon. BUT, a lot of people rather not consume it if they had a choice due to the many negative effects of the chemicals if taken in rather large portions which in most cases highly unlikely. The only reason why we do add preservatives is to maintain the freshness of the syrups that is being served since syrups will spoil extremely fast if not well preserved. So, it's really your choice to add or not to add it within your syrups. Which most people do I would think or at least in the concentrates that is being used to form the syrup.