Not to be contrary, but if the Bisley is available, and you really want one, I would get one while you can. SAA's are always available from USFA but the Bisley seems to be one of those items that are done in limited production runs (someone correct me here if I am wrong). It might be some time, depending on sales, before they start producing them again. If you wait, they might not be available when you are ready to buy that second gun, whereas you will always be able to find a 5 & 1/2" SAA (if not an inspector series, at least a similar pre-war model).
Another point in the Bisley's favor - there are a whole bunch of USFA SAA's out there and only a limited number of Bisleys.