In my opinion it is a catch-22. I truly enjoy the iphone for its smoothness and fluiditiy. As much as I detest the saying "it just works", the iphone in my experience is a very polished and efficient device that works well. With that said, I believe this has a great deal to do with the fact that apple does not allow the user to customize core functions via third party apps. I don't have any facts to back this up other than my experiences, but I found that the more I would customize these features (gallery, keyboard, sms app, launcher, etc) on my android devices (most recently the GS3 and Note 2), the more lag and issues I would have. Not too mention the lack of ease I would feel every time I offerered up a boat load of seemingly unnecessary permissions in order to access these third party options but that's for another thread.
In the end, I would love to have options on the iphone similar to android devices, but not at the sacrifice of stability and fluidity in operation. Now, if it were other factors causing my reduced experience aside from the customization, then my feeling is invalid. But at this point, I dont have any reason to think differently.