Or create each image separately and draw with
Another advantage of using a Sprite Map is the fact that canvas already supports drawing 'sliced' images. When drawing an image, you can define a sourceX & sourceY as well as a targetX & targetY. In my engine this is exactly how I handled animations.
"To measure is to know" as the saying goes. Try both methods and see what works.
Drawing each image separately
A texture atlas is a large texture that contains all smaller textures used in (a section of) the game.
Most likely you'll end up with a combination of the two techniques: a texture atlas for small, static objects and high-resolution images for your dynamic objects.