What is your seq setting? SD DV will be about 2.3GB, ProRes SD will be about 3.2 GB. IF you are working with DV I would do the PAL in DV. If you are using HD or something better than DV I would go to ProRes.
But the other things you need to be concerned with is the NTSC to PAL (if that is something you are going) It is not a simple change the settings and reexport. Compressor can do it but it is know to only do a so so good. Nattress Filters has a standards conversion that is really good for software.
Then different frame rates are converted differently. If you are working with 24p you normally just retime the video and audio to PAL’s 25. Also PAL using lower field first for DV but upper for everything else. (I know it did for tape and I’m assuming it does for files, may want to check that)