What I dislike so far is that my files appear in three separate places, rather than just one, and especially if I use the »managed« option, I don't see any point whatsoever in the Files bit of the interface. As a mental model, the reason behind splitting Catalog and User Collections is not clear to me, why is this distinction useful to me? I can't see any purpose behind it –*although that doesn't mean there isn't one. Perhaps you can help me out here: where do the equivalents of Aperture Projects live?
I also use the Managed Option like I did in Aperture... Capture One Catalogs are identical to Aperture Library files. They are an elegant way of hiding the messy file structure and makes it easy to backup or move your photos. Of course, they are just package files so you can right-click and choose "Show Package Contents" if you want to get at the insides.
Structure: C1 and Aperture are more alike than different... Both programs support Albums, Smart Albums, Projects, and Folders. Thus whatever structure you have in Aperture can be duplicated in C1.
Attached are a couple of screen grabs of my structure in both applications... (identical)...
The key difference between them, is that in Aperture, you can import photos, or drag and drop them into Projects. In this way, Aperture's Projects and Albums are the same. In C1, you cannot put photos into Projects, only into Albums. Otherwise Projects still work the same as in Aperture in that they allow you to browse all photos in the underlying Albums... but they don't actually contain any photos. So, in Aperture, if you were in the habit of storing photos only in Projects and not using Albums, you will have to make an adjustment when moving to C1... Albums are where you need to put your photos now... not in Projects. You can still use Projects to group Albums and set the scope for Smart Albums, but you can't import or drag and drop photos to Projects.
As far as seeing your photos in multiple places, I don't think this is different...
Both apps have a section at the top of the Library tab for managing the catalog (all images, recent imports, trash, etc.).
In Aperture, a photo in my "Trips > Paris > Street" is visible in all three of those structures, as well as when selecting (All) "Photos" and/or "Last 12 Months" and maybe even "Last Import".
In Capture One, a photo in "Trips > Paris > Street" is also visible in Paris, and in "All Images" and in "Recent Imports" which is almost exactly the same as Aperture.
The only difference is that Capture One has the "Folders" brick which you can collapse if it annoys you (I believe it's for those not using Managed Catalogs).