Not really biased, both are my favorite characters. Though there is not possible way to know if he is able to realize he is in a gen quickly, most of his actions in the fight against Tobi and Raikage show incredible split second reactions and strategies.
Well, then we go "why Tobi didnt caught him in gen?", the reason may be because he didn't had the time to activate the gen. Minato will not stand still and let Itachi take command of the fight, he will take the first charge. As you have seen, Itachi was trying to lay eye contact on Sasuke before, and he needed to turn his eyes at quick speed even with 3T, Minato's speed will be as hard to see as Bee's eight sword style. Do not under any circumstances over estimate the sharingan, it was enough to slow down the speed of naruto in one tail, but Minato has faster spontaneous movements (though he wouldnt win against naruto in a race, Im just meaning his spontaneous acceleration from one side to another is faster).
At last, I never said Itachi was slow, I was just saying that he is not even near what Minato is, though he still holds his ground as a fast character.
