I still really have no experience with those flavors personally, but the brand will help you when looking at other's recipes or getting info on a particular flavoring. One brands pecan (just as a loose example) maybe very different from another's.
Many times similar flavors are used together to get a fuller flavor, strawberry is a good example. I don't often see a recipe with just one type of strawberry.
Some companies also have different versions of the same flavor marked Version1(v1) or Version2(v2). V1 tend to be the ones with potentially harmful chems like diacetyl and others. They also tend to have a richer flavor than the V2 flavors, which were made to be "safer".
Amounts of potentially bad stuff in V1 flavorings are not a big concern to many, they are frequently also found in much greater quantities with
tobacco. Others don't want that potential harm regardless, understandably. V2 flavors can taste good too.