Are you sure?

The m7-6y75 MacBook scores about 6800 multicore in geekbench, which is equivalent to a maxed out MBA and a mid-high MBP 13 from last year.
Now think about i7-6560U and iris 540...
The 28W U series processer is only used by few OEMs and Apple now.
Look into the history, the 13" MacBook (pro) had been using 35w C2D T-series chips untill 2008, when the 25W P-series came out. That was the time when 15W ULT SL-Series C2D was just born and very weak, stays on the MBA until Sandybridge 15W ULT came in 2011, which gives MBA a huge boost in performance.
For now the preformance gain form 28W U does not pay off the extra power consumption form extra wattage. Untill 28W QC come out, the 15W U is the way to go.