I’ve used Solidworks for 15 years, and I think Onshape is close to as good for modeling, and now much better for collaboration and version control. Collaboration is great, but version control and configuration management is the killer feature of online CAD tools. These also facilitate typical collaboration which is at a part level more often than part level. The existing tools rely on a lot of discipline and are very hard to set up and maintain, and generally requires people assigned full time to maintenance (or full time to manually handle it in the filesystem). On the other hand, Onshape does not allow engineers to invent their own workflows.

For a software analogy, the existing tools are like sharepoint at best and cadfile_v2_final(Mike).prt at worst. Onshape (and I assume other) online tools are like github.