Hhm, I think you might have attached the same image twice. So I don't see the problem either.
Just importing a file into Inkscape, and saving it, doesn't magically make it a vector image. The SVG format can contain both vector and raster content. So if you imported a raster image, and saved as SVG, what you have is a raster image inside the SVG file. So it never has been vectorized, and of course is still pixelated.
If you're using the Paint Bucket tool to fill in color, surprisingly, that tool still works when you use it with a raster image! That tool does leave a small gap of unfilled area. So I might guess that you're seeing a sliver of the raster image, between the color applied by the Paint Bucket tool, and the enclosed area.
If you look on the Paint Bucket tool control bar (just above the horizontal ruler) you'll see a Grow/Shrink setting. However, it's not perfect, and there will always be areas where it doesn't fill completely, and maybe even areas where the color extends outside the enclosed area. I always have to tweak the new color object with the Node tool.
Which vector format is best, depends on what you're going to do with it. Why are you importing the SVG file into GIMP?