^100more hp and almost 300 more ft lbs usually makes a difference. 2004-2015
Stock LB7 @ 300/520, same trans compared to the 8.1 especially if it was 4.10s, I’d put my money on the Vortec 8.1 in the 0-60 and drag strip.
But the LB7 would still out tow it.
Nevermind that $300 would get your Dmax into the 400/900 range in about 10 minutes of install work.
Your comparison is wholly not applicable, or at least no more applicable than saying a 70s/80s smogger 454 is slow so why run a new gasser with double the horsepower.