Cores Vs speeeeed PPD?

[ubersonic]

I didn't want to jack another thread but this post about hex core Xeons stood out to me as its something I have been wondering about:

Not worth buying unless you're going to get 2 of them, and even then, it's just 12 slow Sandy cores, but can be done on the cheap I guess. Can't help but think you'd be better off getting a 3930k and taking it higher, 6 cores at 4.4GHZ are going to beat 12 at 2GHZ surely?

What is better for PPD speed or cores?

Lets compare these two:

Xeon E5 2650L - 8C16T, 1.8GHz (8 core turbo is 2GHz), 20MB.

i7 3820 - 4C8T, 3.6Ghz (4 core turbo is 3.7Ghz), 10MB.

Both are socket 2011, both have a 2.5MB cache per core ratio, both use Sandy Bridge architecture. The only differences are that the Xeon has twice the cores and half the speed (more than half under turbo clocks).

To make it simpler lets assume the i7 is clocked at 4GHz as any chip can do that and it means the only difference is the Xeon has half the speed and twice the cores. Which would get the better PPD? or would it be virtually even?

Thanks