What exactly will newer/more expensive autopilots get you?
I mean other than more features they all run the same firmware… What can you expect from getting the latest greatest hardware?
Your question is extremely open ended and hard to answer. To generalize to an extreme, more modern hardware will allow you to access the full potential of the ArduPilot ecosystem, including more robust filtering, scripting, additional peripheral hardware support, more bandwidth for peripheral data, etc. When choosing an autopilot, you should probably have some idea of what support is necessary, such that you don’t needlessly spend money on advanced hardware or accidentally budget too little for hardware that won’t satisfy intent.
Personally, I go with the more expensive autopilot options (such as the CubePilot) because of the increased quality control. More expensive autopilots are also generally more powerful and better suited for future iterations of ArduPilot.
Agreed. I am a huge fan of the Cube Orange at present and look forward to trying other H7 variants as budget/needs allow/dictate. I can’t imagine using ArduPilot without a robust Lua scripting environment, which necessitates the more advanced hardware.
All good answers…
I started off with a clone pixhawk 2.4.8…
And just got a pixhawk 4…
I learned a lot just setting up the cheap clone but quickly found out that it was limited in alot of ways.
But after buying the holybro (pixhawk 4 isn’t that new) I wonder what a F7 offers other that the pixhawk 4 doesn’t?
Will it fly better?
Will it be more stable?
Will it do my dishes? 
(full disclosure, I currently have a project on the go with a Pixhawk 4 and it was an upgrade from a 2.4.8)
In my opinion, if both boards have the same firmware and are both properly setup, then on a good day I don’t think you’d notice a difference between the flight characteristics of them. Start adding sensors, or more complicated features, then the F7 boards are going to shine. Often higher end boards will have more built in redundancies and features like vibration damping and IMU heaters. For many DIY users that may not be worth the expense or provide any operational benefits.
So what do you want to do with it? Personally, I have planes and quads that fly just great on F4 boards and there’s no plan or reason to upgrade the controllers. At work, (outside of training projects) we use F7 and H7 boards only.
Without a decent IP rating I don’t recommend using them for washing the dishes, but Cubes with the IMU heaters may be good for drying.