If you don’t do anything CPU or GPU intensive, stick with last year’s M1 Pro or Air. They will give you longer runtime. But note that they have some inherent limitations to external display support and GPU performance that prevents them from doing certain things well.
In my case, I edit a lot of photos and do 3D modeling as well on top of trying to drive an external 5K display. The M1 would choke as soon as I try to push 3D models @ 5K resolution. It makes sense. The thing is just not that powerful.
I have an M1 Pro 14″ now and it is… indeed just what I need to be able to do 3D modeling at 5K. I certainly could reduce resolution to what the M1 is comfortable with, but then… what’s even the point?
On top of that, the M1 Pro is 2x as fast as M1 at exporting >100 photos, and also 2x as fast at slicing my 3D models for the printer. I also occasionally run audio simulation with 3D spectrum and waterfall graph analysis, and the M1 will choke a lot when it comes to that while the M1 Pro can easily handle it. All of those tasks are more CPU dependent than GPU dependent. The 14″ easily does all of that while still easily lasting between 10-12 hours for me. M1 would also only last just that long if I was pushing it that hard.
But during light use, I must admit, the M1 MacBook Pro 13″ that I have would easily last around 15 hours or so. It’ll easily last even longer than a single work day and longer than my iPad Pro 12.9″. Also its performance should be fast enough for most other tasks that don’t involve hardcore 3D work.
So again, I think you should get one of last year’s model and save your money for something else. But if you can afford the extra $$$, and you want to be able to do all of your tasks pretty much about twice as fast as M1, then go for the 14″.
This pretty much sums it up: (note that M1 is slightly faster than the Core i9 but it’s not that much faster)