I've now tested both of the types of Capture One Sessions that David Grover shows in the live stream video discussed above, namely a "Standard" Session and a "Utility" Session.
Testing has reinforced my view that the video doesn't address the subject of this thread, and that the video may not be well understood. At the outset, I want to reiterate that the video was made the day after PM6+ was released, that Grover says in the video, in response to a question from a participant in the live stream, that he doesn't know what PM6+ is, and that his video has nothing to do with Photo Mechanic Catalogues.
The video shows use of Capture One Sessions rather than a Capture One Catalogue because Grover believed that photographers using both Capture One and the standard version of Photo Mechanic together are likely to be engaged in the kinds of photography where Sessions are commonly used. The first sentence in the video description says "Photomechanic is a popular choice for photographers working under pressure in the field, certainly with events, sporting events and photojournalism." The example photos that he uses in the video were made by a photographer who specialises in pro sports events.
Capture One Sessions, regardless of attributes, require one to create a Session parent directory. However, my understanding is that the subdirectories that Capture One generates when a Session is created - Capture, Selects, Output and Trash - represent nothing more than a suggested workflow. These subdirectories can be renamed to whatever one wants. Their very use is optional. For example, many photographers do not use the Selects subdirectory. If I recall correctly, Grover himself has said that he doesn't use it. Furthermore, photographs don't even have to be within the Session parent directory.
Unsurprisingly, Grover first presents Capture One's suggested Session workflow, in which both the Capture and Output subdirectories are used. This approach creates a self-contained package that makes a lot of sense to assignment photographers who need to share their work with others. Grover then presents a modified workflow for photographers who want to create a Session that is used as a revolving door.
In this workflow, one creates a new Session. Grover calls it "Utility Session".
With this Session active, one then creates a new directory for the photographs for an individual event, in his example "Super Bowl 2020". Note that this directory is created from within the Utility Session, although it can be made wherever on one's computer one wants. The idea is that one will create a new directory for each event photographed, whether it's a football game, a wedding or a vacation in Patagonia. Note that this new directory takes the place of the Session "Capture" subdirectory.
The final step takes place after one has used Photo Mechanic to apply metadata to the photographs destined for this new directory. From within Photo Mechanic, the photographs are copied to the new event directory. Grover offers two ways of doing this so that the PM metadata is retained.
Capture One is then used to process the photographs. The processed photographs can be exported to the "Utility Session" Output folder. However, Grover suggests that one stay with the event directory that has the original photographs in it. This is done by creating, within the event directory, a subdirectory for the exported files. No doubt some event photographers will find Grover's suggestion attractive, but it may be less attractive to photographers who need to share a full Session package.
I've now tested both of these types of Sessions with the same original photographs, and examined the resulting files in Mac Finder. Considered in the context of a single photo event, there is no substantive difference between the two types of Sessions. They result in exactly the same files and exactly the same amount of data.
However, Capture One takes the position, correctly in my view, that a Capture One Catalogue makes more sense than individual Sessions if one is creating a body of work rather than recording discrete events such as a wedding, a product shoot or a football game. Grover's video doesn't address users of Capture One Catalogues at all. That's because he thought that the main market for PM6 was event photographers. A reasonable assumption on his part.
There is a related issue, not addressed due to the video's immediate focus, of considerable significance. It is not possible to do a search among Sessions, regardless of whether we're talking about Standard Sessions or a revolving door Utility Session. Over time, this workflow results in a large and growing number of self-contained, inscrutable packages of data.
Remembering that Grover's video was made before PM6+ was even a consideration, how does one address that? Grover's answer would be to import one's Sessions into a Catalogue once the short-term desirability of a Session workflow has passed. An additional step if a Session wasn't needed in the first place.
I think that it's clear that PM6+ adds overhead to use of Capture One. How much is less clear. As @ahoward says three posts above, one can create a PM6+ Catalogue that doesn't create proxies. This may be attractive if off-line access to the Catalogue's images isn't needed. I tested both settings, and turning off proxies does reduce PM6+ overhead.
For me, it's important that Capture One, both in Catalogue and Session views, shows me the current processed state of photographs rather than the unprocessed originals. I still need to investigate what's involved in getting PM6+ to do this. Hence my July 4th post in this thread about a 2016 Camerabits video that talks about achieving this with Lightroom.
My next steps are to address that issue and its resource implications, and to test using a Capture One Catalogue and a Photo Mechanic Plus Catalogue together.
