I like the appearance of the Cosmos,but that is just me.The benefit of the Millenia is having a separate motor,which would be easy to service,as well as a bit less noise introduced into the plinth.
Don't get me wrong,as there are numerous fine products out there,but virtually anything SOTA is going to be superb,and the vacuum feature is just fabulous,IMO.
This is a very conservative company,and they are concerned with keeping existing customers happy.They have thousands of units in the field,due to their long history,so that gets the most attention.
One reason why they don't(need) to really advertise much.
Reviewers' jobs are to keep us abreast of what is new.That is just fine,but new does not mean better,and it "does" usually mean more expensive.
Good luck