In another thread, I documented a battery test that concluded that the M3 will typically last about 14% longer than the i5/4/128. Despite that advantage, I'm leaning towards the i5. Here's why. Faster - Everything seems to happen a little bit faster. It's not a huge difference, but it's noticeable. For example, the M3 takes about 15 seconds to start up from Hibernation. The i5 takes about 10 seconds. Better sound - I know this doesn't make much sense, but the sound from the speakers is definitely better on the i5. I can't imagine why a faster CPU would result in better sound. It could be simply the variation in manufacturing. So, it comes down to quality time vs. quantity of time. Five hours of usage is probably ample for my needs. I would like 14% more battery time. But I'd rather enjoy the time I have more, than have more of it.