Virtual box: i5 or i7?

I was asked to recommend a CPU for a friend who uses virtual machines a lot.
Budget IS an issue, but performance is more important. (Would be willing to pay 30% more for a 15-20% gain)

So, what's better for using several VirtualBox VMs?

I'm not really sure about the amount, it could be about 2 or 3, or maybe up to 6-8 vms at the same time (it would depend on the performance itself, probably: the faster, the more vms).

He won't be overcloking, probably.
So, should I tell him to get an i7, or a very similar i5 (just no HT)?
 
Thank you for your answers.
Budget is a big issue, actually, so Xeon is not possible.
There won't be overclocking either, because of the added cost and reduced stability, and the fact that he doesn't know much about PCs.

I'm looking at these CPUs (price is in my currency, but just for comparison purposes):
i5-4690k ---- AR$3350 (same price as non overclockable)
i7-3770 ----- AR$4000
i7-3770k ---- AR$4250
i7-4790 ----- AR$4500
i7-4790k ---- AR$4900

The price of the whole system would be about AR$10.000

This is to give more details on the question.
He will probably start with 16gb of ram, and down the line upgrade to 32.
 
https://www.virtualbox.org/manual/ch03.html#settings-processor

"3.4.2. "Processor" tab

On the "Processor" tab, you can set how many virtual CPU cores the guest operating systems should see. Starting with version 3.0, VirtualBox supports symmetrical multiprocessing (SMP) and can present up to 32 virtual CPU cores to each virtual machine.

You should not, however, configure virtual machines to use more CPU cores than you have available physically (real cores, no hyperthreads).

On this tab you can also set the "CPU execution cap". This setting limits the amount of time a host CPU spents to emulate a virtual CPU. The default setting is 100% meaning that there is no limitation. A setting of 50% implies a single virtual CPU can use up to 50% of a single host CPU. Note that limiting the execution time of the virtual CPUs may induce guest timing problems.

In addition, the "Enable PAE/NX" setting determines whether the PAE and NX capabilities of the host CPU will be exposed to the virtual machine. PAE stands for "Physical Address Extension". Normally, if enabled and supported by the operating system, then even a 32-bit x86 CPU can access more than 4 GB of RAM. This is made possible by adding another 4 bits to memory addresses, so that with 36 bits, up to 64 GB can be addressed. Some operating systems (such as Ubuntu Server) require PAE support from the CPU and cannot be run in a virtual machine without it.

With virtual machines running modern server operating systems, VirtualBox also supports CPU hot-plugging. For details about this, please refer to Section 9.5, “CPU hot-plugging”."

More cores means you can split CPU usage and still get an effective CPU in the Virtual Box. Xeon is the cheapest way of getting more Intel cores.

or FX8350 for amd build.
 


What sites are you looking for parts at? If you can afford an 1150 i7, you can definitely afford an 1150 Xeon V3 CPU. Considering Xeon v3's are i7's without a iGPU, to me it's a no brainer. A Xeon 1231 v3 here in the states goes for about $230. The same price for an i5 4690k.
 
Where I live that Xeon (and any Xeon that would fit into 1150) is either impossible to get, or just way too expensive. The only ones I could find are:
E3-1220 ----- AR$3300
E3-1225 v3 - AR$7900
E3-1241 v3 - AR$8900

So, no Xeon for this build.

Just to answer the question, the site I'm looking at is www.mercadolibre.com.ar , the equivalent to e-bay in my country (only looking at new products). Where I live we can't import products from international sites, and there is no official retailer.


So, in conclusion, given the price difference, if usage would be demanding enough, and given that he plans to keep the same system for 5+ years probably, an i7 would be a nice investment, right?