Spock Prime, as Jim called him, missed his time dearly. Of course, being able to revisit his youth alongside his friend's counterparts was a blessing he thanked Surak for daily. But, as much as he valued them and watched over them as best he could, they were not his friends, and the differences between them were hard to ignore.
The McCoy he'd known and served with was not as sarcastic and surly as this one; Joanna was a common feature in conversation with the other McCoy, whereas this one was still too broken from his divorce and separation from his daughter to speak of her often.
The romantic implication between his younger self and this Uhura had surprised him, and he'd assured both the young Jim and his young self that no such feelings had existed in his time. It would have, he'd said, hinged on incest in his time.
Thankfully, the two Scotty's were much the same in both times, except the one in his younger self's time did have a rather curious fixation with sandwiches, but he supposed that no one was perfect and accepted the brilliant Scot all the same.
This Chekov's only difference from his own was that this one had been affected on a much deeper level by the stigma of a child genius that his own had. It was seen in how defensive he became whenever someone questioned the calculations made by a 17 year old.
And this Sulu, though he had the potential to be a phenomenal pilot, was just not as experienced as his own had been. Though, if it hadn't been a potential 'game changer', as Jim would say, he'd have warned him to routinely brush up on his manual flying.
The biggest difference, the one he felt every day, was in Jim. In terms of captaincy, the two were near identical; compassionate, follow-your-gut, do what's right and hang the consequences. Off hours, they were much the same as well; either reading or playing chess or just watching the stars from the observatory. What made them so entirely different was that his Jim had never let himself bring their feelings into real life, while in contrast, this Jim thrived on letting people know that Spock was his as much as he was Spock's.
Whenever he saw it, it made something in him burn with something akin to jealousy. As much as he loved his Jim, that openness between them inspired a tiny seed of hatred and resentment. They could have been together in another time.