I don't know who makes the "best" as I have not tried them all. But I'll tell you what I have tried and what I have found.
A.) New stock mounts from GM. Nice quality, allowed engine flex, but "wore" out over time (8 years of abuse)
B.) Energy Suspensions inserts. Nice quality, allowed a little less than stock flex, and were working the same as day one when I sold the truck.
C.) ORD's mounts. Excellent quality, allows a slight bit of engine movement (Have mounted an SBC and now BBC in them) even while truck pulling it keeps the motor pretty steady. Some people said I would feel alot of vibration, but I have only noticed a slight increase during daily driving (nothing I would complain about as it's the nature of the beast). I had them in there for 4 years abusing them with my SBC and when I swapped in the BBC, they looked good as new. The only issue I have had with them is lining up the motor mounts to the engine. They are designed to be rigid so elbow grease is involved. I have found leaving the bolts loose where they attached to the frame mounts, can aid in easier installation of the motor.
The first time I did it, I bought longer bolts and left them loose. Installed the motor, tightened the bolts and then replaced them one by one with shorter bolts (because I'm anal). I could have left the longer bolts and it would not have mattered though.
If you are planning to keep the vehicle for any length of time, I would go poly inserts (Energy Suspension), and if you are going to put a monster motor and or do truck pulls, etc. I would go ORD.
That's just my .02
