How much bulk can you tolerate?
Is the weight of your bag important to you? If it is, it’s best to go with the smaller iPad Pro. The slight difference in weight is negligible on paper. However, when you get a case for your iPad and add a few items to your bag, every gramme counts. No matter what iPad you pick, if it replaces your textbooks and notebooks, even the 12.9-inch iPad Pro is much lighter.
Your Workflow
Is your iPad Pro going to be your only productivity tool? Do you use a laptop, another iPad, or books? For those using the iPad Pro for both textbook reading and note-taking, the 12.9-inch model is a better choice. It has enough screen real estate to maximise the benefits of split-view. The bigger your screen, the bigger your split windows. It is much more comfortable to split view on a 12.9-inch than a 9.7-inch screen.
The 12.9-inch iPad Pro is also better for those that work from one workstation, typically working from a desk 90% of the time. The bigger iPad Pro is too heavy to carry around all day. You should consider the smaller iPad Pro if your work involves a lot of movement. The smaller iPad Pros are better for reading while commuting or sitting on a park bench. They are more portable. No matter how much you love your iPad Pro, you will feel ridiculous studying or reading from a 12.9-inch screen on the subway!
I strictly use my iPad Pro indoors; at home, in class, or in the library. It looks ridiculous during hospital rounds. It’s making me feel like I need an iPad Pro mini. Seriously! It is tiring to carry it around the hospital wards.
If you have a laptop or are still using physical textbooks (because your university isn’t paperless yet), the 10.5 or 9.7-inch iPad Pros will work well for you. Their screens are big enough for note-taking without split view.
Your Budget
It would be impractical to ignore this fact, even though not much can be said about it. The bigger iPad Pro costs more than the smaller one. Unless you really need the big screen, the 10.5 and 9.7-inch iPad Pros will do just fine.
The size of your iPad Pro doesn’t change the capabilities of your device. Both sizes function the same. When split viewing your apps, size mostly adds comfort. If the price is too steep, the bigger screen is a convenience not worth straining your budget. Besides, the 9.7-inch iPad Pro (and all the iPads smaller than 10.1-inch) get a free Microsoft 365 subscription for life! This is an enticing offer if you need Microsoft 365. $7/month for the rest of your life is a bit much.