In either case the pH will be very low with ro water and it will take forever to cycle the tank. Beneficial bacteria grows much faster in hard alkaline water than soft/acidic water.
IME, Africana is crap and falls apart on you very quickly, although it won't leach nearly as much ammonia at the beginning.
Ammazonia is great though. You'll definitely want to cycle the tank with tap water. Once it's ready for shrimp, you can start adding ro and remineralizers.