Well... Im gonna build a rather large airbox around the carbs and seal it as best I can so getting a good vacuum to run a PCV setup will be near impossible, plus Im not too keen on getting oil vapor in my combustion (ever 10th of a HP matters.)
With the old motor we just ran both to the catch tank... but if the valve cover breather is good enough for all ventilation, then running one line to the catch can simplifies everything, cleans up the engine bay and even reduces weight (ever little bit helps)