Raster images do not need to be rendered - see Rendering:

Rendering is the process of generating a photorealistic or non-photorealistic image from input data such as 3D models...Today, to "render" commonly means to generate an image or video from a precise description (often created by an artist) using a computer program.

Note that "render" is a fairly generic term, and it is sometimes used like "render to the screen," to just mean to display something. Rasterisation may be a better term to use here, since it only applies to vector graphics, and is the part of the process I am referring to.

In any case, except for possibly reading fewer bytes from disk, the vector case includes all the same compute and memory cost as the raster image - it just has added overhead to compute the bitmap. On modern hardware, this doesn't take terribly long, but it does mean we're using more compute just to launch/load things.