virtualbox and vmware are the easiest to use, but which one uses the most resources and is there a way to check the resources used?

My guess is they would be about the same on a current well supported hardware base and OS. There would be no clear winner I'd think. I run them both and don't notice much.

Run one at a time and use tools like top and system monitor tools to discover what runs better.

That's a bit of an odd question considering the nature of virtualization...the resources used by the virtualization software are nothing compared to the resources used by the guest OS. Do you really care if VB uses 10 MB more RAM or 20 MB more disk space than VMWare (or vice versa) when the guest OS is eating multiple GB of each? If you're concerned with performance differences, that's a different matter entirely (and that's a very odd way of phrasing the question), and there are plenty of performance tests online comparing different hypervisors.

It could be useful I guess to a new user or one that has extremely limited resources?

Since they are basically the same in the way they work and are used they don't compete well. Looking at other projects may compare better. ESXI maybe or KVM to XEN or other platforms