Fri May 08, 2015 3:52 pm
"switch" means that the routerboard has a hardware switch chip for wire speed forwarding at layer 2.
"bridge" is the CPU-based bridging of frames at layer 2, and it will probably not come anywhere near wire speed unless you have a very powerful host running RouterOS.
Since the KVM host is virtual, it has no hardware for switching ethernet frames, so it is only able to use CPU bridging.
This is the difference and it is indeed a very important "special" meaning.