comparing videos

[tasosss]

Hello.
I own an osprey 460 and a magewell PRO CAPTURE HEXA CVBS.
My input it from set-top box dvb receivers.
I want to test those 2 cards in order to find out which one
is quicker than the other.
I have used h264 encoding with ffmpeg.I have added a timestamp (the local machine's time , displaying milliseconds and syncing both machines with ntp) and then i compared same frames(im not so sure about that) with the time that was displayed.Of course i don't think that this is the right way.
I suppose i have to use raw video,without any encoding.
I tried to use virtualdub2 but 1) i can't add a filter 2) i can't find a filter to display time.
My question is simple.
Which is the most accurate solution for such a problem?

ps: Some advices from https://forum.doom9.org/showthread.php?t=162466 seem interesting but there are no more info on how to do it.