the difference is
a 6.0 sounds like its in a state of failure from start up
the 6.4 is quiet
when i bought my 08 there was a 6 L beside it
both running at the same time and i couldnt hear the 6.4

oh and the 6.4 pulls a ton
not as good as my cummins but it pulls good

The Series Sequential Turbo's Are Just A "little Difference" Between The Two :tttt:

its a day and night differance on the power end of it i had the 6.0 i liked it but it was always broke down