hdman,
I've had the 6.0, the 6.6 and the 8.1 in a burb. They all have their good and bad points. However, you wanted to know about racing stock trucks. When there new it's really close. The 6.6 will be the pig, the 8.1 will be a pig and the 6.0 will be 95%. Once they all have say.... 20k the difference will increase. The 6.0 parts, 4L60 trans ect, are lighter than the 8.1 burb, 4L85E trans ect, and the Duramax, Allison ect, which plays a role in the race. {reciprocating mass thing}
Ok, here we go................
1/8 th mile----- 1st= 6.0 2nd= 8.1 3rd=Dmax
1/4 mile.... just reverse the order.
However, if you're just "kick'n it" from a run, the 8.1 will probably out run the lot.
If you would.........why the question?
Burner---------->