Pros and cons of bowline

Hi! As a climber new to sports climbing (but not to trad) I´m beginning to understand why we use a bowline to tie in. But I note that climbers use a great variety of methods to back up the knot, such as an extra fishermans or a doubling of the loop part of the bowline. I´d like comments on what seems to work best, and I´d love to see references if there are any official sources or tests. Thanks John