My name is Matt and I’ve been using Blender for over 10 years. Today I came to understand the difference between subsurf vs multires. I’d like to share that information with you now.
Subdivision Surface is a modifier that adds virtual geometry to your mesh, giving it a smoother appearance. The extra geometry isn’t there until you apply the modifier. The extra geometry is added evenly, across the entire mesh.
The multiresolution modifier adds editable virtual geometry to your mesh. The extra geometry is editable in sculpt mode, allowing you to add finer detail to parts of your mesh, leaving other parts untouched. You can step up and down the different levels of resolution, retaining selective detail.
Best Use Case? Which One Do I Pick?
Most of the time, I use Subsurf. It’s just a general, quick way to add extra geometry and smooth out your model. Mulitres is best and almost exclusively used for sculpting. Once you get that extra detail in there, you can use that high poly Multires model and bake out a normal map to toss into your material. TLDR;
Subsurf: general smoothing.
Multires: specific to sculpting high details and baking later.