iPad Air M3 vs. iPad 11th Gen for study/notes

Hands down, the iPad Air M3 is technically the better option - providing significantly better flexibility, features and capabilities as your needs develop over time. Some of the significant differences have been mentioned by sberman. Both of your listed iPad models can, as outlined by Phil0124, be reasonably expected to have a similar support lifespan.

Whichever iPad model you choose, you would be well advised to purchase as much internal storage as your budget might reasonably allow - as internal storage (and other hardware) cannot be changed, upgraded or extended. The available internal storage is fixed for the entire life of the device. If you run out of internal storage for your documents, photos and other data, you will forever struggle and become a source of frustration. It is far better to have more storage than you need, than to need more storage than you have.

A good rule of thumb is to quantify how much data storage you will need - add a healthy margin - then double it. If you are unable to quantify your data storage needs, it becomes more difficult. Whilst I and others cannot make definitive recommendations for your personal needs, objectively I would council against purchase of any iPad with any less than 256GB storage, 512GB and higher having a greater margin for growth.

Within the Apple Support Communities we see regular tales of woe and disappointment when storage requirements are exceeded, necessitating replacement of the device; by contrast, we never see complaint of having too much available storage. It is relatively easy to fill limited internal storage space; perhaps consider higher tiers of storage as providing room for growth as your needs develop or mature - potentially extending the useful usable life of the device. 

Also consider the functional differences between WiFi Only and WiFi+Cellular models of iPad. Aside from the obvious Cellular functionality, only WiFi+Cellular models include GNSS/GPS location capabilities - which may impact any Apps or features that require accurate and consistent location data, such as Mapping. 

Purchase of a WiFi+Cellular model provides access to precise location services, but does not commit you to using Cellular connections. WiFi Only models of iPad have no Cellular or GNSS/GPS functions at all.

Both the iPad Air M3 and the iPad A16 (11th gen) were released at the same time, March of 2025, so will have a similar life span in terms of software updates and support from Apple, around 5 to 6 years. Not being sold by Apple does not affect this in any way.

Both will fulfill your needs fairly well. Yes, the iPad Air has the better processor and better screen. Wireless keyboard support should be exactly the same. For en external display the M3 iPad Air will support extended desktop, which allows different apps to exist on the external display than on the iPad's screen, while the A16 iPad can only be mirrored to the external display.

As for storage, you can always pair it with an external drive, and move out large files to the external drive.

The Files app can let you access files from external drives pretty easily and directly.

Photos, Music, Movies and Books in Apple's and most 3rd party apps will however will remain on the iPad and cannot be moved.

I’m thoroughly enjoying my new 12.9” iPad Air. I had planned to get new iPad Pro but when I saw the price difference I walked out of the Apple Store with the Air under my arm. I also planned to pick up a new iPad but with the new price increase my old iPad will have to last a bit longer.

If you’re still unsure go to the Apple Store and spend some quality time with both. The answer will become rapidly evident which one to get.

In your list of feature comparisons, you omitted the facts that the iPad Air M3 supports Apple Intelligence and it supports the Apple Pencil Pro. The iPad A16 (11th Generation) lacks these features.

As you correctly noted, the iPad A16 is currently sold by Apple while the iPad Air M3 is not, making the iPad A16 more “future-proof”.

If you are thinking of buying a used iPad, you might want to read this:

The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community