Well simply put they are optically the same. However the CFi current lenses have a few different features most of which will not produce any imaging difference that the eye can detect except in the most extreme uses.
Probably the most significant issue for some shooters in that the current CFE lenses offer data-bus connection between lens and camera. BUT, the current 150mm you are looking at is a CFi so it does not have data-bus connection anyway.
So, the differences between CF and CFi are:
The barrel and grip design differs - some think this CFi design is nicer. It makes no difference to me.
The internal barrel coating of the CFi lenses is new and said to be more resistant to stray light - enhances contrast. Most pros agree that unless shooting in extremely high key uses, the eye cannot see the image difference.
The CFi lens shutter spring is made of a new high-tech metal thus said to extend the life by many decades - well the CF spring is likely to outlast most of us. I understand that the CFi spring can be retro fitted to a CF lens anyway.
The lens mount is a nice unpainted high-tech metal so never shows wear. No real benefit that I can tell.
The filter bayonet is also made of the nice hign-tech metal - resists the paint wear on the CF lens hood and filter bayonets.
Finally (I think!), the CFi has a X synch cord locking fitting on the lens designed to avoid accidental disconnection. Some CFi users complain that the lock device is plastic and too fragile.
So there is no compelling reason IMHO to buy CFi over CF. There is no optical design difference. The choice comes down to relative value between the 2 as far as your personal budget is concerned.
In my case all my lenses are CF except for the 80mm CFE that came with my camera body. To my pocket CF is much better value for money - I get mint used lenses for much less than nice CFi/CFE versions. My CF 150mm is excellent.