The firmware includes that functionality, in a way. With iOS, there aren't that many applications that you can get from the official App Store that will remain running when you minimise them, even if the application remains resident in memory.
And if Apple have approved an application to run when minimised, you can bet that it meets battery consumption requirements. I've had quite a few applications minimised and never had a battery consumption problem.
I think you'll find that Apple does pretty well with battery life altogether, honestly. It's not going to be a problem unless you jailbreak it and install a bunch of stuff without really thinking about what's going to be running all the time.
You might be able to find some particular test or another at which a high powered Android device might seem faster.
When you have a moment, though, you might want to look up some Youtube video of reviews by reputable personnel who are currently comparing the iPhone 4 to devices like the Galaxy and the new dual core devices built on the Tegra 2 (the LG Optimus 2X will be easy to find because it's about to hit retail stores).
http://www.youtube.com/watch?v=NSuRwn1RBPM
That is the phonearena.com browser comparison.
It seems to me that the iPhone 4 compares well to the very latest generation dual core devices and super-GHz devices, and I have to say that in day to day use with my iPhone 4, I do not in any situation notice any time that I'm lacking the power to do what I want (relative to its being a phone, after all).
And I am a pretty heavy user.
I only have experience with the GSM iPhone 4 on AT&T, of course.