Exporting PAL SD material to MPG4 from FCP7

I have a pile of SD material that was ingested into FCP 7 some years ago. It is in 720X576 and I want to export it for web download/stream in MPG4. My problem is if I export in FCP7 file "Using Quicktime conversion" and select MPG4/ H264 and 3000Kb/s the quality is great, but the time taken to do this is 4 hours for an hour of material. If however I send to Compressor and choose the lone MPG4 option, the operation only takes only an hour but the quality is poor. Im not sure why this is so dramatic, I know the max bitrate I can select is 2048Kbs but it doesn't explain the dramatic difference.

My version of Compressor is 3.5.3 so its quite old & explains why the bitrate choice is so slow by modern standards. This Mac is still on Lion so I presume I can't upgrade Compressor. Can anyone suggest a way of getting good quality MPG4 in less time on an old machine like this?

PS I have about 200 X 1 hour shows to convert, hence the urgency regarding processing time.