From an end-user point of view rendering engines are mostly indistinguishable. On the other hand the whole UI and speed of loading of pages are very much notice

From an end-user point of view rendering engines are mostly indistinguishable. On the other hand the whole UI and speed of loading of pages are very much noticeable and this a developer can directly control. Note I agree that what Apple does is bad, but claiming that it prevents differentiation where it matters is simply not true.