DSR80 has an option for SDI output -this would be the best way right into the AJA I/O SDI input, but the Sony DSR-45 has analog component outputs, and this would be the best way to transfer into the I/O.
In my opinion, it is always better to capture using the AJA I/O (or AVID Adrenaline, or Blackmagic card, etc.) ALWAYS instead of going straight in via Firewire. Others will disagree with me, saying that there is loss going thru converters.
You can use BOTH VTR's (DSR45 and DVCPro50) with analog component, into the AJA I/O. As I stated, may DVCPro50 VTR's have SDI outputs, and you will get excellent results going SDI out into the AJA I/O.