What is the best iOS version to use on a fourth generation iPad?

As has been stated, your only option is to install iOS 10.3.3.

You cannot install any other iOS versions, other than the current version for your iPad.

iOS 10.3.3 should run fine on your iPad 4.

You just will NOT get ANY of the really cool whiz bang features, like two screen multitasking and some of the other features that require an iDevice with better hardware specs.

In my opinion, the best versions of iOS for older iPad models were iOS 6 and 7. iOS 9 wasn’t bad, either.

iOS 8, IMSO, much like the current iOS 11, was one of the "not so good” iOS versions.

I avoided upgrading any of my iDevices to iOS 8, then and I will be, probably, avoiding the current iOS 11 for all my compatible iDevices, as well.

Good Luck to You!

JR wrote:

Well, now I can't see a way to edit my question so I'll try this to do a bit better job of asking it. I currently have iOS 8.4.1 and understand I can go to 10.3.3. What I am trying to ask is what OS version works best on this machine. I have learned over time with computers that the latest OS that a machine will accept may not be optimal because it simply bogs the machine down.

The question is moot since with your iPad 4th at the moment can only update to iOS 10.3.3 and nothing in-between.

iPad 4th generation came with iOS 6.0.1

At the moment, you can only update to iOS 10.3.3 max.

My family has a 3rd generation which is running 9.3.5 (the latest it will support) and a 4th generation with 10.3.3 and both work as well or better than they did with earlier iOS versions.