Taking the video via firewire will maximise your video quality and the ease with which you edit your video. Ideally your work flow would be capture via firewire on MAC > Edit and Output on the MAC.
That means you'll have to find another way to put a timestamp on your video in post production. I know that there are various ways you can do this on a PC, but not sure about a mac. What is the reason for the timestamp?
Take a look at these links:
http://www.skydiver.de/stef/datecode_en.htm