Hi dsaavedra,
there are numerous uses for both items. The crackleback dry fly (Bob Story from Feathercraft is the originator) is tied using the turkey or goose biots and AK Best video has numerous patterns using the quill body for dry flies. The results are beautiful flies that are more durable than dubbed bodies and give the fly the appearance of a segmented body as are the naturals. I usually give the quill body flies a coat of Sally Hansen before using them as a means of strengthening them. The biots can also take a coat of Sally H. depending which side of the biot is used. I think it takes a bit of practice to work with these materials as the quills require presoaking and the biots can be fragile if the thread tears the biot during the tying process. The AK Best videos demonstrate tying with both materials. If you are a learner, I really like the video's because they can be stopped and replayed as needed. With an instructor, it is a one time deal and then you are relying on memory. The biots can also be used for tailing on nymph patterns such as the Prince nymphs or other stone fly patterns.