The journalizing of filesystems typically only protect the metadata-portion of the filesystem. In the case of virtualization, the whole filesystem of the guest is considered data to the host OS. So in the case where you'd need journalizing, it doesn't help when either the host-filesystem itself or just the client FS gets corrupted.
Also, the overhead of journalizing is neglectable compared to the IO losses you have simple by virtualizing, which is magnitudes larger (if you get 50% of your original IO capacity to the guest, you are lucky, with plain VirtualBox, you probably get only ~30%). You shouldn't worry about the journal here. Thus my advice is: always use a journalizing filesystem.
Another point to mention is the time to restore in case of a crash. One of the most important tasks the journal fulfills is to ease recovery in case on an unclean shutdown. If you use a journalizing filesystem the time used be the mandatory
fsck is going to be magnitudes smaller than on an unjournalized filesystem. This fact alone might be a deal-breaker if you need halfway decent restore times.
When you actually need IO, at least use a Type-1 Hypervisior (like Xen or KVM), which makes it easier to get to the 50% (or even a bit more) of remaining IO capacity, or use application-level virtualization like OpenVZ which only uses a minimal amount of resources itself.