the 24% was 24% better frame rate, so yeah you will notice, its going to be the difference between tearing on games and not tearing, or if locked, 60 and 30 fps, not on all third party games but on a great deal of them yes.
So unless devs try to add more effects on PS4 to even out the frame rate between the two consoles, you are going to notice big differences in frame rates, much bigger than in the current gen, just as you would with 2 similar spec'ed PCs.
Carmack was talking about similarity in architecture, and work flow there is going to be no tearing up the rule book for devs this time.
Again these are 2 identical PCs next gen but one has a faster graphics card with faster graphics memory, you really have to be burying your head if you dont think there is going to be a visual difference in frame rate on multiplat games.
