This subject usually sparks a lot of debate. Nobody has published an official study so far as I know. Least of all Sierra for the reasons stated in some of the threads...
Who uses SMKs for hunting?
Why do you use SMK bullets for big game?
The biggest difference between the 142 SMK and the 140 Berger is the word "Hunting" that Berger stamps on their box.
Regardless, a whitetail or antelope hit with a well placed 142gr SMK travelling at 1800+ fps is going to be in serious trouble.
I may just give the SMK a try next season.