I havn't tested either, but Looked at their particular web sites. Berger advertized .528 BC and didn't list the velocity. Sierra Listed .505 @ 2800 fps and above
.496 between 2800 and 1800 fps
.485 @ 1800 fps and below
.
Dirtball is correct in that your gun may not shoot one or the other very well, but according to their claims the Berger has a slight edge on BC. However, Sierra gave much more detailed information which makes me feel it is more likely very close to the actual BC. Sierra's are exceptional bullets.