Does the iPhone 6 need to be thinner?

I saw the leaked photos the other day of the alleged iPhone 6 (Air?) and I got mixed results here on this forum regarding the width and height but one thing is undeniable, it will be thinner. I personally like this design because it is what I have been saying Apple needs to do since I bought my 2nd gen iPod Touch. Super thin and sleek.

Thing is, someone on here stated that the phone doesn't have to be thinner. More thickness= better battery life. They could go wider and taller for more apps but that means more retina pixels to push which means it needs a bigger battery. So should the iPhone 6 be thinner? If they add an entire row of apps at the top and side, that gives it a LOT of room for more battery and you could possibly get a 24 hour battery life. Thoughts?