Just a quick thought that occurred to me as I read the OP: I’m less about apps and more about principles. Those constraints provide some productive limits on app-switching.
I’ll write a few examples below. It’s not a conclusive list, just an off-the-top-of-my-head set of ideas.
A first principle: I want files. My mental model of how my workflows work emphasizes finding the content or materials I’m working with and opening those in any number of apps, not opening the app and then finding the content I wanted to work on. For this reason, the iPad lifestyle has always been fraught for me—recent developments in Files and apps as file providers are nice, but they’re still not perfect.
This same constraint leads me to like deep linking. If it’s easy to build links to the content, then I might be able to tolerate a file-less workflow (e.g., Craft, Roam). But still, I prefer being able to identify a file somewhere.
A second principle: Markdown. The content I work with needs to be able to be written in Markdown. I’ll export to docx or whatever as needed, but the more markdown, the better.
A third principle: I need a little bit of the right kinds of friction. If it’s too easy to add content, but not easy enough to manage it, whatever I’m putting into a “workspace” (i.e., an app + the content it works with) becomes noisy as heck and, inevitably, unusable. A great example of this is Concepts (iPad). It’s an incredible artwork/sketching app, but it doesn’t sync (!?) and interacting with previous sketches happens through a horrid UI. I used to open it all the time, but as a result of the buildup of cruft, I’ve moved away from it.
OmniFocus/Things/etc. are another example of too little friction. I quickly fill them up with wishes, not actions. Kourosh Dini wrote about this problem recently. Whenever I use a hyper-powerful task manager, it feels great for a week or two and then I end up feeling like I’m moving deck chairs around a titanic. I’ve since switched to managing my projects and actions in markdown (I know, right) and I’m much better at maintaining what I’ve got to do with integrity.
So, choosing apps may be the wrong way forward. Choosing principles or approaches and letting those define what tools you can use might be more functional.
Another giant throwaway: remember that we shape our tools and, thereafter, our tools shape us. Make choices (about tools, and everything else!) that reflect who you want to be.