Adam.
Your question has no true answer, there is no such thing as the best flavour size make of boilie. For example the best baits I have ever used do not contain any flavour in its true sence. Boilies are just another food source. Buy Carp talk or another weekly publication and see which baits keep croping up. Pick one and stick with it. There is no such thing as a super bait or a super rig, it is location and bait application that catches carp. Observing carp and learning how to use a marker float set up, will catch you far more fish than the latest bait on the market.