A lot in my opinion having used diff android phones before. Is that whole thing about fragmentation. It helps android in sales, if they can make ten million diff android phones. Where it hurts is the os. It's nearly impossible for android to simulate the same exp on each phone. Cause each phone has diff features and specs. That is where rooting and throwing your own rom comes in. Of course not every user wants to do that. But for those willing to try and be patient to customize their phones, I'm sure it is something they love as a whole.
How do you define 'the same experience'?
Feature wise, there really is little to no difference. The hardware inputs are all exactly the same. The difference with speed are legitimate, and I'd expect a $100 cheapo Android device to be slower than a GS4 or a HTC One, yet all of this 'Android lag' BS is based on this completely irrelevant comparison.
The onus isn't on Google any more. Project butter really worked. My last Android device was a HTC Desire, I went to iPhone 4S and am now using an HTC One, and Android has come on leaps and bounds since then. What does need to be addressed is the skinning. Skinds like Touchwiz and Sense do affect the overall experience, and the OEMs need to really take a look at the value, if any, they're adding, as it does put more load on the CPU, but the latest handsets out there show that there's plenty of power to cope with whatever is thrown at them, and they can perform well.
I do not, however, consider Android or iOS to be better than the other. Provided the hardware and software combination is fast enough, and the apps I want/need are available and working, the OS is good enough.
Long story short: If you buy a cheap Android handset, it'll probably lag. If you buy a GS4 of a HTC One, it won't. If you compare a cheap Android handset to an iPhone 5, you're an idiot.