I think these guys have posted some really valid information but if u want the large BOV sound go the manual as the auto just shifts into next gear and the turbo beings to spool where with the manual, when u go to change gear, it slower, the throttle body shuts and the larger amount of compressed air is let out through the BOV hence, pffft! lol, i own a manual GTS skyline and am just about to have a conversion done (read my thread in N/A section) but i agree, a skyline is a skyline, go with what u can afford and if you don't mind driving an automatic then don't worry about what others think, you can trick up both manuals ans auto to run good times and perform well.
Hope this helps, Hame {sorry for long post}