Can you elaborate more on what is your workflow, what do you want to actually achieve etc?
It really depends on what you're doing on iPad / MBP.
What amazed me the other day on the iPad is 120Hz screen. Really astonishing.
The simple but important stuff.
I could do much of what I do on an iPad if I was to re-work the way I do things. Right now I keep my photo library distributed on local storage and NAS. I'm not sure how the iPad can work in that environment, since the file management is almost non-existent. I could just buy a high capacity iPad and use iCloud to solve many of my photo workflow issues I think. I'm assuming LR on the iPad can do HDR etc. So from a photography perspective (and it's just a hobby) I think I can make it work, by materially changing the way I organize my data. So I suspect I could make that work, but it would be a significant amount of change, moving libraries, organizing data etc.
I also record through GarageBand on my MacBook. I know I can do that on iPad too. I also distribute my storage there too between local storage and NAS, so would have to change to a cloud based model. I'm not exactly how I would interface the iPad with my gear. I actually do use an iRig on occasion with my iPad, I have both the analog iRig and the USB based iRig and multitrack through an audio interface into the MacBook. I'm pretty sure I could make that work with an iPad Pro too. I'm not 100% sure, but I'm 95% sure. Again, it would mean a significant change in the way I organize my data, but I'm sure it's possible.
Office stuff - I have to have a keyboard. Luckily the iPad can do that too. I love using the iPad for reading, but I don't like the on-screen keyboard for typing more than a few words. I couldn't imagine using it for heavy work, that would be torture. Easily solvable.
Pulling photos off my camera. Right now I use SD. Also possible to get those onto the new iPad via the right cable I believe. 99% sure I'm ok there.
iTunes - I'd move to Apple Music, that would make sense and be easy, but of course I would incur costs.
General surfing and reading - no issue.
So the vast majority of stuff can be done. I'd have to materially change the way I handle my data, and get a large cloud subscription.
The larger challenges.
PS4 Remote - I can use my MacBook to play my PS4. Currently no answer to that, but that's not a huge deal in any case.
Other stuff - there are random things that I do on my MacBook that seem to be easier than on the iPad. I imagine a lot of that can be done on the iPad too if I buy the right apps. Wifi survey, can that be done well on the iPad? Not sure, but maybe.
Financially.
An issue is that he largest iCloud package is 2TB. I could make that work right now but that wouldn't work for me for long. I have a 2TB NAS and am about to upgrade to 4TB. But by culling older data I could work with 2TB. CAD$12.99 for 3 years is $467. The 512 GB iPad is $1,699. So that's $2,166. Over $2,500 if I factor in Apple Music. I'm not using cloud based Lightroom yet either, so I'd need to also include that. Maybe that's unfair at this point since I'll likely need to do that on my MacBook eventually, so we're pushing $3k if we include that. Can't keep using LR 6 forever. I'd also need to increase my Internet bandwidth. I use local storage so I don't need a large Internet connection at the moment. I have 40Mb/s down and 10Mb/s up which is great for gaming and streaming Netflix, but if I was moving to a cloud architecture I'd probably want to increase that. Over three years let's say that's another $750, but I'm probably being a little conservative there. So let's leave out Lightroom, but with the additional costs for iCloud, Apple Music, and increased Internet speeds, that's perhaps $3,250.
$3,250 - That's going to buy a pretty nice MacBook Pro. If I was buying a brand new MBPro today it would likely be the 13" nTB or the 13" Quad Core. Both come in well under $3,250. I'd want to spend perhaps $1,700 - $2k.
That's not a detailed financial analysis, obviously, but it's not a slam dunk. I could go with a cheaper/smaller iPad of course.
But again, for most of what I do the iPad will do it, if I make material changes to the way that I work. That's a lot of money AND a lot of change, and that's certain to bring pain.
I considered moving to a tablet as a primary device before buying this MacBook Pro. I'll likely replace this in 12-18 months and will consider moving to a tablet then too. For those little occasional tasks where I really want to have macOS I can just keep my MacBook Pro around (I previously had an iMac, which is obviously not portable).
So really it's very close to being something that I could do, but it seems that it would end up costing me more. A lot more. The gap widens if I stretch our my MacBook Pro from 3 years to 5 years. 5 years of extra costs for Apple Music, iCloud, and faster Internet sway the equation further.
All the price I quoted are Canadian.