Many thanks for this in-depth comparison! I have yet to test OF but have rigorously tested Things during the last couple of days and found quite the same issues as you, Niels, annoying, to be frank. It surely is heavily related to your own life but there are a couple of features missing where I cannot draw any other conclusion that CC folks have VERY different life and brain settings compared to mine.

It begins with the simple fact that you cannot create a project in the inbox. You can start a task and assign it to an existing project but honestly: how far from reality is that? First you decide to throw a party, next you break it down into steps or sub-projects – not the other way round (send invitations, buy beverages, organize music etc)
This brings me to the weakest point of Things: the lack sub-projects and the lack of connecting tasks that are interlinked, where one task cannot be executed before the other one is completed. Most projects do comprise “sub-projects” and hence, it is inconvenient to handle these via workarounds rather than a solid, integrated solution within the app. No offense to the guy above who suggested having less projects: it may have been your solution but does not address at all the desire of folks like me who just love electronic support in handling their projects and strive for the best suiting GTD app.
Similar to Niels’, my projects are a mix of daily recurring tasks and to dos that occur only once or a few times per project. It’s therefore bugging me that again I have to create workaround in Things.
Bottom line:
I need to thouroughly test OF and may not be perfectly happy with it but Things disappointed me. The interface is seductive but the options are really limited, and workarounds if at all possible are time-consuming to create, maintain, and clutter the system further up. “Form follows function” is my motto but with me and Things, it would be the other way round. However, the investment in an app should pay off by supporting and facilitating my daily work which Things failed to do.
Off to download OF now …