what about the speed? which is more speed between L2 (Trunking) and L3 (rouring)?
That's an "it depends" answer, including factors such as how you define "speed" and the capabilities of the actual hardware.
With modern hardware, assuming the hardware doesn't need, for some reason, to "punt" a packet, likely the only forwarding difference between L2 and L3, the latter may have some additional latency. Much older platforms, doing flow based L3 forwarding would have higher additional latency for the first packet of a flow.
I want to emphasize that any latency differences between L2 and L3 forwarding are usually so small that almost all the time it doesn't matter to typical networks. For example, would a 1 microsecond delta matter to your usage?
BTW, you might also find forwarding latency differences between different hardware platforms.
Simple example, even for just L2 forwarding, the latency difference between traditional store and forward switching and cut through switching. Or the difference between fragment free cut through and not fragment free cut through switching. All three forms of L2 switching may be wire-speed/line-rate, and the same "speed" if you only consider bandwidth, but not the same "speed" in time needed to deliver data.
