How do they spy on you? There's no suspicious network traffic leaving my Mac. They might collect info about Siri queries or downloaded apps, but they're certainly not logging keystrokes from OS X or iOS.
Microsoft is capturing text input and handwriting from touch input interfaces the same way Google's Android keyboard , Swype, or Swift Key do to improve predictive input, spelling correction/suggestions, personal dictionaries etc. Remember Windows 10 is touch enabled operating system like iOS or Android.
I'm not as familiar with the Apple Keyboard but I would be surprised if it didn't do that too in some form. Their Quick Type feature states it performs heuristics locally but it doesn't mention other aspects. Their policy states they don't collect personal information or conversation history but that doesn't mean they aren't capturing corrections or things they deem to be non-personal but sound pretty personal to me (e.g. occupation, language, zip code, area code, unique device identifier). Remember how researchers were able to identify Netflix users based on lesser anonymized meta-data? That non-personal information sounds pretty damn personal in comparison.
I hope you're not using a 3rd party keyboard on iOS with Full Access enable because if so then you agree to the same thing Microsoft is asking for.
I'm surprised you're ok with Apple recording Siri Queries and sharing them with Walk N’Talk Technologies who has humans listening to them but you're opposed to Microsoft doing anything similar in Cortona. How do you feel about Google Now? Did you ever use Google 411 because that was just a quick way to get a massive archive of audio samples.
> Their policy states ... but that doesn't mean they aren't capturing corrections or things they deem to be non-personal but sound pretty personal to me
> sound pretty personal to me
It's pretty clear actually. What you may think about situation may have zero factual grounding. You'll need to provide some citations and references instead of just saying what you think or feel the situation may be.
On their QuickType page they say "your conversation data is kept only on your device, so it’s always private." That's a lie because iMessage and your keyboard Dictionary are synced to iCloud which isn't your device. That doesn't mean that it's in Apples hands or they can access it but it's not a factually true statement either. They're also careful to say "conversation data" and not something more general like "anything you input into your keyboard".
I'm not suggesting Apple does anything more invasive than anyone, I'm just suggesting they don't do anything less based on what's observed.
Is it opt-in or opt-out ? Because I use iCloud for Safari bookmark sync only and it never bugged me for syncing anything. Local iTunes encrypted backup is fine.