I'm not so sure I'd be dismissive of a processor on clock rate along. Different architectures allow for different numbers of operations to be completed during each clock cycle. Its why modern 2 Ghz CPU's will flatten old school 4 Ghz CPU's.
The Haswell architecture in the new Pro has big advantages in energy efficiency, but is less stellar in situations where the CPU has to run at full load. Might even use more power under those conditions...but that's basically gaming, video editing, rendering, that sort of thing. Daily office tasks and internet stuff are going to net you a serious battery life improvement while also probably a decent performance improvement. Plus you get the HD5000 GPU..which is way better than the 4000.
Haswell is awesome for anything that runs on a battery. Apple is getting a solid 12 hours of battery life from their new MBA and also better benchmark scores. Intel is kicking ass!
But...desktop is way better regardless.