Difference Between two 6.0's

I have a 2004 Silvy 2500HD, the engine code in the VIN is U. There are two 6.0 engines listed in the book. I believe they are Q4 and L9 but don't quote me on that. But my question is what is the difference between the two? I'm new to the EFI engine world and want to find out all I can about this new generation of engines.
Thanks

I have a 2004 Silvy 2500HD, the engine code in the VIN is U. There are two 6.0 engines listed in the book. I believe they are Q4 and L9 but don't quote me on that. But my question is what is the difference between the two? I'm new to the EFI engine world and want to find out all I can about this new generation of engines.
Thanks
As LQ9 engine is what is used in the Silverado SS, in the Silverado VHO (mine), and in the Cadillac Escalade. The LQ9 engine is a 10 to 1 compression ratio instead of a 9.? to 1. The LQ9 engine produces 345 hp and 380 ft. or torque.

The other engine you listed is used in the 3/4 ton trucks and Chevy considers this engine their "standard 6 liter engine". It does not have the high output compression and as a result produces less hp but still plenty torque.

To my knowledge - both of the 6 liter engines are known for their dependability and durability.

Thanks for the info. Appreciate the reply. Now I can call it a day, I learned something.