I would have to say Apple. Their OS has been well rounded since day one. Im not biased in any way as I currently own a Galaxy Infused 4G. The reason iOS is so responsive to touch is because that's what the whole os is designed around. When you make a gesture on any iOS device, the os immediately minimizes any other processes and prioritizes your commands. Android does not, therefor even if you have a powerful dual-core android phone you still will see lag. Google has been getting better with their os but it's just not all there yet. Also it should be personal preference, do you want a device that you can put widgets on the homescreen, highly customizable, syncs flawlessly with Google services (gmail, calendar, ect.) or a well designed os that has the largest appstore, excellent build quality, doesnt slow down over time, and has tons of accessories (docking stations, car stereos with iPhone/iPod control, cases). But if you were going to go with iPhone I would suggest you wait for the iPhone "5" because the current iPhone has been the same design for almost two years now and there is a new one in development.