It's a lot down to a. personal taste & b. the types of waters that you are fishing that particular fly on. There's only one hard & fast rule, there's NO hard & fast rules.

Different styles work for different people. Many years ago I remember reading something by Dick Walker. He said he arrived at a fishery & was starting to fish where one guy had just left. Dick put on a pheasant tail nymph and within 2 casts had a fish on. The guy who had blanked at the same spot came & asked him what fly he was using etc & apparently had been fishing a pheasant tail nymph there for 2/3 hours without a touch. It could be down to presentation or any number of other factors.