The Criterion is the winner here.
The BFI has noiser audio, burnt in subs on a transparent background (as you see on TV sometimes) - albeit with a less slangy and contorted translation. And though the picture is sharper they fucked something up as there are green and purple tints to parts of the image throughout so it's not really B&W. There are also the lines top and bottom.
They both have the same Geroge Lucas extra only it's NTSC>PAL on the BFI transfer. I've a feeling BFI uses the same master for the film itself as Criterion but buggered things up thereafter.