When the Win 8.1 preview was first released I attempted to install it in the latest version of VirtualBox but it was a no-go so I tried the free VMWare Player and it installed without a hitch. A few days later, VirtualBox released a newer version and I was then then able to install Win 8.1 preview there. The same thing happened back when the first Win 8 Customer Preview Release came out, it would install fine in VMWare Player but not VirtualBox until VB was updated.
I think VMWare does a better job of keeping up with things.
At any rate, Win 8 & 8.1 (both 32 & 64 bit) can be installed in the latest versions of either product.