This is no one, single best tool for bounce flash, because the desired end-result of lighting varies so much. Shooting bounce flash in a 25-foot-high church interior is one thing; shooting bounce flash aboard a yacht or cruise ship with an 8-foot high ceiling in a tiny room is another issue. In the church, you'd likely elevate the ISO to 500,640,or 800 or even higher, and zoom the flash head to 135mm beam spread and try to get a good, solid bounce by throwing up a precisely-directed, narrow beam. This was at one time called "foofing", by famous wedding pro Denis Reggie, and became popularized back when the Canon 5D series offered good ISO 1600 to 3200 results for many people who had what was then, cutting-edge ISO performance and image quality. Loooooong-throws, like 30,40,50,60 feet throws to the bounce area, and using wide apertures, like f/2 or f/2.5 or f/3.2 on a prime lens, and high ISO levels...that is one,specific type of bounce flash: High ISO, wide f/stop,long-throw bouncing at distances wayyyyyy longer than you can do at ISO 200.
Aboard a ship or in an apartment living room or in a hotel bathroom, you have the polar opposite situation: the bounced light has very rapid fall-off, due to the very short distances. The rate the light falls off is terribly rapid on a short-distance bounced lighting set-up...within a foot, you can have a 1.5 or even 2-stop fall-off, and the top of the picture area can be very hot, and over-lit....this is the type of situation where say, wedding shooters often find themselves with the bridal party and the groomsmen...in a small, cramped area, where they want to use bounced flash, and where the Fong diffuser or other omni-directional diffuser makes on-camera, simple flash pictures so much more evenly-lighted. Typically in a very cramped location, you would want to use a wiiiiiiide beam spread of light on the bounce, not a narrow one!
There are a number of different flash picture looks too. Direct-flash on bracket; flash + 5-inch parabolic reflector+ diffuser; Sto-Fen tilted up 45 degrees at close ranges under 12 feet; there's so many ways top shoot flash, that there can not possibly be any type of universally appropriate flash accessory. There's also a difference between "pumping up the ambient" by firing a shrouded [flagged off] flash (Neil's technique and BFT approach), and between firing a flash that directly hits the subject. There is NOT one, single thing that is a panacea.
Like Big Mike wrote, above: "So the key with any flash accessory, is to first understand light. Understand how flash works and how you can balance it with ambient light etc. With that knowledge, it should be fairly easy to know when to use which accessories, and just as importantly, when not to use them.
Of course, as with everything, it's always a compromise. A smart photographer chooses their gear to balance convenience and functionality, and does what they can within the limitations of those choices."