I used 5.25% sodium chloride ("bleach") until last year but have switched to a a refillable 20 litre carboy that I get filled with 12.5% sodium chloride (super bleach ).

From what I figure I also calculate that your bulk price is lower than buying jugs of bleach. It really should be too since you are providing the container and the 12% stuff is bulk shipped to be refilled.

Each is just as effective, it depends on how the prices in your area. Like you, the bulk is cheaper for me. Plus with the higher concentration I don't have as much liquid or bottles to handle. To do it again though, I would have bought 2 10 litre carboys instead. The 20 litre container can be cumbersome.