You need different kind of tools. The is no one "magic" tool, which suites to all tasks. For board bows and clear staves cutting tools are just great and comfortable to use. With good axe, hand plane (bench plane no. 2 or 3) and/or spoke shave you can do anything you want. I have fine-tillered many bows with spoke shave only, so no scraper. In fact, after buying a good (and expensive...) spoke shave I don't need scaper so much. With sharp spoke shave you can cut as thin shaves as with scraper. But the cutting tools have to have a very sharp blade, otherwise they are useless.
A (thick) scraper is valuable tool when you have knots or irregular grain or very dense and hard wood. I prefer scraper when tillering ipe-bellied laminates, when hand plane or spoke shave would tear wood.
I need rasps occasionally, usually when I have very problematic knot or something like that. Tillering with rasps is tricky in my opinion. And it makes a lot of mess and dust. There are many kind of rasps - traditional rasp, shinto rasp, surform, microplane or iwasaki rasp (like a float). After using all of them, I prefer iwasaki rasp. It is relative cheap, fast and produces very fine surface. You can use scraper after iwasaki, which is unusual with other types of rasps.
With soft woods I prefer cutting tools and hard woods I use cutting tools always when possible and if not, then non-cutting tools, i.e. rasps and scraper. So, the best tools depends what you are doing, and where. For tillering, I like the spoke shave, iwasaki rasp and scraper is the best trio. But you do not know it before you have tried...
