I have a project which involves material shot with DVCAM and DigiBeta

I have no SDI facilities and was considering format conversion of the DigiBeta tapes to DV for editing

The end product will be DVD (about 1 hour full bandwidth)

question is since the final product will be DVD how much subjective loss will there be between

1 DigiBeta > DVCAM > MPEG2 (8Mbit)
2 DigiBeta > MPEG2 (8Mbit)

anyone with real experience with this issue?

The weakest link in the chain will be the MPEG2 encoding. The bit rate is kind of high. It sounds like software encoding. Most commercial DVD's are hardware encoded between 4 and 6 bit and are of excellent quality, as you've probably seen.

Lower quality encoding will wipe out any quality advantage the beta footage might have had. However, high quality encoding may reveal weaknesses in the DVCAM footage and footage converted to DVCAM.

Video footage acquired with very high production values will convert and encode the best. If all of this sounds rather vague, it is. Without more details about your project it is difficult to provide specific answers. You might want to try some sample footage and look at the results and see if they meet your expectations.