I’m one of those who use only components. I do so because I can leverage the benefits they have over groups. My primary application for SketchUp is drawing woodworking projects for proposals and construction plans. Even if there’s only one of something in the model, such as a table top or chair seat, invariably there’ll be at least two of them by the time I get finished. I absolutely want changes made to one instance reflected throughout.
With components I can:
Immediately give the part a name.
Set the component origin and axis orientation to make applying textures and component insertion easy and painless.
Easily create small parts and avoid the issue of holes created due to too small geometry.
Many people make groups first and convert to components if they wind up copying it later. Or at least they try to remember to do so. We see requests periodically from users asking how to convert a couple of hundred copies they made of a group to instances of the same component because they forgot to convert to a component beforehand. I avoid that problem from the git-go.
We also see complaints from folks who’ve forgotten they are modifying a component instead of a group and discover all copies of it got the same treatment. I always know I’m editing a component and know if there are copies of it in the model space so it’s never a problem to remember to use Make Unique when needed. (I assigned a keyboard shortcut for Make Unique so that’s a simple thing to do.
As I work through drawing a model, I tend to use components to batch operations much like they’d be batched in the shop. For example with a model of a table with tapered legs, the tapers are typically all the same so while all four legs are instances of the same component, I would add the tapers. The front and back legs might get different joinery details, though so before I draw those details, I’ll split the back legs from the front with Make Unique. I keep them related as long as I can, though to reduce the work.
I think the best thing for efficient work flow is to maintain consistency. Of course that’s just my idea and not everyone needs or wants to do that.Fortunately, SketchUp is flexible that way.