VB-settings: how many cpu´s?

I would like to install Opensuse 13.2 in the Virtualbox, in win7 (64bit) host. My computer has quad core (i7 Q820) and 20 Gb Ram.

  1. Is opensuse 32 bit more stabale in the VB then the 64bit version?
  2. Is it better to sett 4 cores for opensuse or let the default settings (single core)? Can I change the cpu settings after installing opensuse?
  1. Nope.
  2. Depends on your needs, I use 2-4 usually and Yes you can change them later on without any issues.

You can always change CPU settings in the Guest properties/settings later if you wish.

But, in general there is no benefit.
Only scenario I know of where there can be a theoretical (not necessarily real) benefit is if a specific app is designed to and requires a specific number of CPU and/or cores.

But, the way modern hardware (and OS) are designed (SMP processing) automatically allocates and assigns tasks according to the CPU’s internal algorithm, distributing across as many CPUs and cores as there are available.(unless you over-ride). Specifying additional cores might in theory allow the app to think there is improved parallellism, but when you get down to what’s happening in hardware it probably won’t make any difference.

Note also that there is no affinity between virtual CPU sockets/cores and what actually exists in hardware, so can’t partition your tasks.