Congrats on your 2010 Chevrolet 2500 HD!
I use the 2" adapter on mine. Seems to work OK and I don't notice any difference in towing. However, now here's another part (the adapter) for you to mislay, leave behind, lose, etc. I live in fear that someday I'll go to hook up the TT, go to where the adapter should be and find it ...GONE! I have enough trouble in this department just keeping track of the hitch pins/clips and locking pins for the trunnion bar chain holders without adding another item to the list.
2009 GMC Sierra 2500HD | Crew Cab | Standard Box | 4WD | Duramax/Allison
2000 Jayco Eagle 266 | FBS | TT
1986 Coleman Laramie pop-up -- Still in the family!!!