4s vs 5s =runtime

[gimpygolden]

I'm looking to buy another pack to use on my buggy and my 1/8 onroad.

I can run either 4 or 5s on both cars,which would yield the longest runtime if they are the same (3700)mah?

I know there would be a significant difference in speed but I am not concerned about this.

Would one run cooler than the other, all other things being equal? ie.gearing,motor