I understand it gets hard to do so but this topic has been covered.
i7 seems to have a growing consensus of 20..30 mins less battery. At least of the threads I have read. TDP is a figure and yes they both have the same but in terms of usage you'll find it varies depending on the tasks you set a given CPU. It can be true that a faster CPU can idle more quickly however a base load drain still might be higher on either CPU, and to be honest I haven't bothered to read the spec on the CPU's in that much detail to say any more
I personally am still ordering an 11" Ultimate. I know I'll need the extra processing capacity over the 3 years of its life, no real option to upgrade or change as it is an institution purchased machine.