I love this scene right here, because each of them has different reactions.
You’ve got One, who’s obviously just insulting them because it means that his incarnation has passed, and that he won’t be “alive” any more.
Then you’ve got Two. He’s happy to see One, and remember all the adventures he was on with Ian and Barbara, and Susan and Vicki and all his other companions. His expression only changes when he hears One’s thoughts on him.
And then we’ve got Three. Three’s expression doesn’t change at all. Because he’s not happy to see either of them. And why’s that? Because they’re free. One and Two are free to roam around the universe, go wherever and whenever they want. And Three misses that. He misses the freedom and resents One and Two slightly, because it was their actions that caused him to be exiled on Earth.
Say all you want about the budgets or CGI on Classic Who, but when it boils down to it, I’d rather have moments like this, little subtle things, rather than great big realistic looking monsters and aliens.