Watts are watts! What you are talking about is watts/work unit or efficiency. Yes the 4770K is more efficient than the 2700K but not by a lot.

Getting back to the two 2700K vs single 4770K output. That is 258 watts vs 142 watts. With power at $.064 a KW here that comes to $63.91 a year extra in power but it also outputs more units. The added bonus is the two 2700K's will crush the 4770k in other work. SOB is one of the few workloads that has a big advantage on the 4th generation core processors.