The reason for this was twofold, I spend more time. unless coding, on iOS tham on Macs, and the integration is just better, no question, secondly while I rely on Gsuite for mail, I really have no need of most of the other features so a move to core Apple services made sense.
Let me clarify this is in no way a denigration of any apps, most of which are top rate, I just wanted to see what I actually needed, rather than what I was told I needed. These so far are my thoughts so far.
First let me deal with the Calendar as it's probably one of the clearest cut cases of where I have been schmoozed into overkill apps. Like many people I was using Fantastical, a great app without a doubt but hang on, do a reality check, I work on my own, remotely, and really do very few client meetings. Yes Fantastical is great, but for me it was a case of having it because I can, Apple's stock calendar app does the job perfectly well for the few appointments or time blocks I need to document. In the same mode I have also ditched the Gsuite calendars and moved everything to Apples ecosystem.
The same also applies to Podcast apps, I listen but am not a voracious consumer, and while I rushed out and bought Overcast, again another great app, for me, again the stock Podcast app is enough.
OK let's turn to the big one Apple mail, e-mail is probably is used more across both operating systems than anything else so I have in the past tried many if not all solutions, none fully satisfying me. For a long time I used airmail, which I spent hours writing custom actions to send stock replies and to send to other apps, but in the spirit of zen usage off it had to go to the trash can. So how is Apple Mail? Well not as pretty, but really quite functional, message rules on MacOS are quite nice, and Gmail rules handle all the heavy lifting of spam, newsletters etc. before the mail actually arrives in the inbox whatever mail programme I actually use. On iOS once I discovered the >print > pinch outwards to share as a PDF to DevonThink I was fine. This coupled with the drag a mail into Omnifocus really has given me a perfectly usable workflow on either OS, and of course the mail app integration with others in iOS "just works" to quote Apples slogan.
I am going to include Workflow app here, now its part of the Apple stable. I love this app, probably only scratching the surface of what it can do, it has allowed me to replace several actions in Zapier I need to run weekly, a task in Omnifocus reminds me to run these, which saves me having to run a paid subscription with Zapier (multi stage zaps cost). I aslo have workflows to create Omnifocus projects and quite a few other bits. What it needs however is a folder/tagging structure and I am hoping this comes with the production version of child of Workflow, Shortcuts, in iOS12.
As for the others...
Notes: Yes I am even using notes, but basically as a way to transfer and access things on both operating systems, most things in here are temporary and I struggle to find a real use given that most saved things live in DevonThink. Once Drafts App comes to Mac I would imaging this will be one app I do not use.
Reminders: No, I use Omnifocus and really nothing else comes close. This is one Apple app which really is of no use to me at all.
Maps: It works, as does Google maps, but honestly I rarely use either, given that where I am at present there are a few main roads and a lot of dirt tracks, no railway or subway and I doubt I will see the Google or Apple mapping car bouncing along the farm tracks any time soon.
So, overall the experiment has been a success, I have not noticed a drop in efficiency as yet and I will stick with this until of course another shiny new app tempts me.