What are the main and most noticeable differences between these 2 models?

NEO = New Engine Option.

CEO = Current Engine Option, which essentially means all prior-to-NEO aircraft. 

So the only difference is the engine?

Basically yes, NEO has also slightly longer range as far as I know. Not noticeable difference in the cockpit layout tho.  

There actually are quite significant differences besides just the engines. Maybe not visually, but I know that they have very different fly by wire logic in certain circumstances. Rotate law for instance was just one feature unique to the Neo which makes handling on takeoff quite different.

That said, it is still a common type rating - but so is the 757/767 and there you're talking wide body vs narrow body!

Edited May 15, 20224 yr by Tom Wright

Overall, it's quite difficult to answer. The main difference is the engines, but there are a lot of systems that are undergoing changes - all the time. So, the longer it goes on the more differences there will be (because A320ceo is no longer produced) overall because not all changes can or will be retrofitted.

Some already in place differences have been told like the rotation law, but there is even more to come. All new A320 will soon get e-Rudder and there will be a whole new generation of flight management to come also to the A320. But there are also a lot of smaller changes that are constantly made due to updates to the systems.

In the end every plane is unique and that is the reason there is official documentation for every single MSN.