Doesn't exactly answer your question, but last year I upgraded from a 3.4GHz P4 HT to a Quad core 2.4GHz and the speed increase in Vue is unbelievable.

As far as I know the quad core will render a lot faster in Vue than a dual core, though a faster clock speed dual core can be faster than a slower speed Quad core for some programs that don't take advantage of all 4 cores.

There is a speed testing thread in the forums at cornucopia that will let you see some comparisons.

My advice though - go for the quad core!

i7 5960X, 32GB RAM, GTX 1080Ti, GTX 980 Ti, Windows 10 Professional.  Running Daz Studio 4.11, Poser 11, Vue Inf 7, Photoshop CS4