Preparing the wood for finishing means getting it all the same as well as getting it clean, smooth, and level.
Sandpaper leaves a scratch pattern in wood.
Different types and grits of sandpaper leave different sizes and shapes of scratches. Scrapers and planes leave still another type of surface. To get a uniform surface, always prepare all areas of the piece the same. If you scrape, scrape all areas. If you sand, sand all areas with the same type and grit sandpaper.