I use P411/TER to window shop and then TER to do background and then back to P411 to actually book.  I store a "gonna see someday list" on P411 - and the contents of that list change monthly.   But it takes a LOONG time with me to go from notice to book.  My personal experience is that P411 is by far the easiest way to book.  Some providers require more information, but at least with P411 you have a consistent starting point.  I have tried some of the other more advertising oriented sites d*techeck, er*s,  - but honestly I think they suck in terms of supplying me with information.  Haven't perused BP for anything other than research in years.  

That said, I recently contacted a provider who doesn't advertise on P411 and doesn't advertise much on TER - and doesn't participate at all on this board (at least as a provider....) but she has been in the back of my mind since 2012...  and the first provider I ever saw was on Er*s and really doesn't like TER at all..