Ok let’s get the bad news out of the way which is that the iPhone 11 and 11 Pro all have essentially the same 120fps and 240fps of the previous iPhones on their main cameras which depending on the phone is two or three. All at 12MP and all capable of 4k UHD at 60fps and all slow motion capable at 120p and 240p at 1080p. So no new frame rates but a consistent capture across all cameras which seems unique compared to the competition.
The real new thing is the availability of 120fps at 1080p in the TrueDepth or Selfie front camera which allows for “Slofies” as Apple calls them. It would have been more impressive to have the full 240fps on the selfie camera too but they will save it for a future model. 120p is good and lets you shoot funny and compelling content. It is probably the best looking selfie camera image we have seen yet so Apple has an easy head start there.