Im respecting Mitrione for his reason's here and I think Jones pulled a punk move and I'll explain why.
Mitrione openly admits that his skills are not on the level of Daniel Cormier and in a round about way admits that Cormier would likely out class him. I think its safe to say that Mitrione would have been a huge underdog here and is trying to be careful with his record. Matt basically says not just no because its short notice, but no all around about fighting Cormier right now. Not ballsy, but I understand.
Now with Jones, why would you turn down fighting Chael when you have been training for Dan Henderson? Jon Jones would've been an even BIGGER favorite over Chael than his original opponent. And yes, people had already spent thousands of hard earned dollars for flights, hotels and tickets to go to see Jon Jones fight but he refuses. Forget the UFC and the undercard guys, the people that got screwed out of UFC 151 were the fans that had spent money planning to go.
Mitrione was offered to take a fight on a card that he wasnt already on and take a huge step up in competition and he said no. He admits that hes not good enough yet. Jon Jones was already set up to fight that day and his original opponent dropped, he got offered an (imo easier) opponent and said no, pretty much because he could. His logic doesnt make since to me. I think Chael could train every day for a year nothing but wrestling, Jones trains nothing but striking for a year, and Chael would likely still not score a take down. Jones didnt take this fight because he didnt have to. And screwed tons of fans by doing turning it down. Mitrione had no obligations for even fighting for Strikeforce, let alone Cormier on that day.
In conclusion, Mitrione and Jones are apples and oranges. Mitrione is admittedly scared. Jones was probably drunk.