Probably the best post thus far in this thread, simply for not just stating larger screen size but what ACTUALLY is being done that needs the larger screen real-estate: workbooks/spreadsheets, resumes (although I did this on a BlackBerry 9780 & Nokia E71i years ago when I have no computer and the later worked much better with the file on device/in-cloud).
Emails - can be managed on any device: composing/forwarding/replying, filing, adding attachments, etc. on iOS attaching emails already downloaded to an email you’re composing seems to be a mystery IF this can be done or not intuitive at all (even on iPadOS). Emails are not a good measure of choosing a single device or any. Mobile email has been around for over 2 decades now, a bad example.
Should the OP or anyone ever need to use their single device to remote control any desktop OS … a phone is NOT going to cut it, period!
Also and most critically … 12/13 mini for a single device.
- really other than surfing the internet, emails, extremely light word editing/composing, music listening, non-professional picture taking/video recording/creation/editing, iOS apps, turn by turn maps, calls iMessage/SMS, or social media (mostly apps really), these 2 devices is NOT the right choice. I LOVE my 12 mini, and I'm still likely to upgrade to the iPhone 13 mini and keep it for 4yrs minimum. But as a single device your screen-on-time (SOT) will be MUCH heavier than anyone typically would since every need for computing or internet etc will be on this device, and unfortunately even with the 13 mini's 1.5hrs average screen time battery life over the 12 mini, its just not enough. Also consider doing your taxes on mobile - this alone is a long process EVEN for someone unemployed+non-self employed and just claiming basic income - doing the taxes still has a lot of silly/dumb steps which you need to complete - I'd guess 20-30mins alone for basic filing. Convenient on mobile but with 13 mini's battery life is just not enough.
13 Pro/ 13 Pro Max if you're on iPhone is your best choice.
I still recommend iPad Mini 6 if you can manage that along with iPhone 13 Pro/Max.