I’m not an iPad Pro user, but I have an iPad Air and I think my experience may help decide, so I’m putting my answer here just in case it’s helpful
I personally have the max 256GB of storage in my iPad Air 4, and kinda wished I sprung a little more money for an iPad Pro with 512GB after some months of having this.
Don’t get me wrong, I love my iPad, but I kinda try and be sure I have plenty of extra space on my iPad when I need it.
If you are planning on keeping this device to use for a while (especially since those models cost between $1199 and $1399 from Apple), I strongly suggest you spring the extra cash upfront to have 512GB on your iPad. The amount of flexibility and versatility you get by having that extra 256GB is massive.
You can see my attached screenshot that I have about 100GB of photos (which I like to have on my device just in case I’m on a plane or I just want to see old memories), which most of my photos are just about 50GB on old trips and memories from those, some are action video clips from those vacations (like snowboarding, etc.), which begins to sum up to around 100GB.
I do own an external USB-C 512GB SSD, but I still try to keep stuff I really want on my iPad on my iPad. I mostly put misc. files that are big storage clogs on my device away from it to avoid completely filling my iPad up, and I don’t pay for iCloud storage at all, mostly because 1) I like to keep the data on me and choose when I want to keep it and 2) I can access it whenever and don’t need to worry if I don’t have internet or something.
I also keep a couple games to play here and there, some internal documents and files in the Flies app (mostly school related and study related via other apps like PDF Expert and Highlights, as well as misc. other files I like to keep around).
I also have iMovie and Premiere Rush which I use from time to time, and other miscellaneous apps like WeatherBug, school apps, Discord, and that stuff has filled up the rest, which puts me at 170GB of 256GB used on my iPad Air.
Depending on when I upgrade, I’m probably going to upgrade to a 512GB or 1TB of storage in an iPad (if my budget allows) just to have the flexibility and almost never needing to worry about it again.
TLDR: I’d spring for the 512GB if I were you, it just allows to store so much more, and not needing to worry about storage too much or having to put files away that you want to keep on your iPad. There’s so much more versatility and will allow you to keep your iPad for much longer and less headache during that time if you spring for the higher option of 512GB instead of 256GB.
Hope that helped out your decision